A  UHS-File and at least two good walkthrus on The Neverhood are posted on various Sites.  Many of the puzzles are fairly easy, but one or two of the solutions are somewhat obscure.  Hence  I add below some further details and clarifications
for any who may need or want them.  They may serve as an addition to the abovementioned (much fuller) Helps!
    If you are really stuck, my recommendation is to try the UHS-File or one of the walkthrus.  If this is insufficient, you may {??} find the solution to your problem below  :~ ))

(1).    'Saves' are not stored in the usual folders or sub-folders but in the Registry of Windows 95/98.  This makes it more cumbersome to store them permanently on diskettes or whatever, or help somebody out by sending them on.  Unless you are quite experienced with manipulating 'Registry Keys' I recommend not playing around with this mechanism!

(2).    A randomizer built into the game alters many parameters, making it impossible to give complete spoilers for many puzzles.  In fact, each time the game is started, or sometimes even when returning to a 'Save' in your same game, these parameters change!  So in the majority of cases, only general procedural solutions can be given!

(3).    A very minor issue :-   During the fairly early part of the game you have to open a door which is locked with 3 dead-bolts controlled by buttons colored reddish, blue, and brown.
    To do this, you have to search all over the territory, and click 3 buttons in different locales, colored orange, blue, and gleaming white .......... A bit of a cop out IMO, especially when you don't know what you're doing or why!

(4).    Quite valid, but caused me a fair bit of wasted time and trouble :-   In many Quest/Adventures you have to press a button or click a switch, etc., in order to progress.  To date, as far as I can remember, once you have done this and happen to return to the same button, it is either completely inert or beeps or whatever but causes no further action or progress (or hindrance!).
    But in this game you have to be VERY careful! Some buttons etc. work on a flip-flop or toggle principle (like a light switch).  If you click once, you have achieved the objective (although you frequently don't know that since you can't see it, because it's a long way away!).  But if you're not certain, which happened to me more than once, and click a second time ('just to be sure'!), you have negated your first action and when you tramp way back to wherever, you've gained ........... absolutely nothing.  Putting it a different way :-  if you click any odd number of times, fine ---- but if you click any even number of times ........ zilch!!  This is rather tough since there is sometimes no obvious connection between the switching action and its distant objective.
    Possibly the most "blatant" example is the specific case of the switches affecting the abovementioned ('distant') dead-bolts.  A "correct" press does create a soft echoing musical tone whereas a 'wrong' press causes a louder rasping buzzer sound.  You are presumably meant to grasp that the former is required and not the latter.  I however did not catch on!   :~ ((

(5).    One of the most infuriating aspects of Neverhood is the "Hall of Records" (Library) where you are expected to read (or are you??) a large number of pages (or clay tablets) which is extremely tedious.  Klayman moves rather slowly, and the majority of the nearly 40 'sections' contains 7 separate pages, each of which has to be scrolled individually.  Unless I miscounted, there are 236 pages in all!  Whether you decide to read them or not (you can readily skip all or part of them!), you MUST get right to the end, since there is one item you MUST acquire there in order to finish the game.  Then Klayman has to plod his weary way back to the very beginning --- no quick or easy exit!  I scanned them all superficially, and to me they seemed to have little tangible bearing on the plot of the game (certainly no puzzle clues of any importance).  For those who are interested, the first half at least seems to bear some similarity to the early chapters of the Old Testament!

(6).    In one section of the game I became (more than normally) confused ... and in case this happens to anybody else, the scenario and a short explanation follow :-
    After Klayman becomes tiny he has to exit the room.  I found this a bit tricky since the room is dark and the small Klayman moves somewhat jerkily.  Near the bottom right corner of the screen is a small exit, not too obvious due to the darkness.  Click on this.  Then click on the large barred window near center screen and little Klayman will walk to just beneath it and look out.  Then click just a very little to the left of where he is standing, and he will exit left to the 'striped column and statues' room.
    In order to achieve ANYTHING  here you first have to return him to full normal size.  To do this you have to fill the Red/Green/Blue measuring cylinders according to what you saw (hopefully) on your putt-putt car travels.
    What added to my confusion was the Orange/Yellow/Mauve cylinders which Klayman can view to the right of the abovementioned window.  These enable Klayman to return to normal size in order to exit the radio room (and doubtless return again later!).  AFAIK, you should ONLY use these if you have failed to find or note the Red/Green/Blue measurements ... otherwise I believe they are completely redundant (and only confuse the issue).

(7).    The Mouse/Cheese puzzle.  I managed to solve this myself by trial and error, but it took me some time and many 'moves'.  Then out of interest I peeked at one or more of the abovementioned walkthrus, and there I noticed clues such as "get the mouse to follow its nose", etc.  To clarify this a little :-
    Each time the mouse emerges from a hole its nose will be pointing either left or right.  Click on the space (not the hole!) next to the direction its nose is pointing.  The mouse will jump towards this space.  Sometimes its nose will still be pointing in the same direction but sometimes in the opposite direction. Either way, enter the hole to which its nose is pointing NOW.  In just 10 moves every time, the mouse eats the cheese and you're on your way!

(8).    Another puzzle held me up for a considerable  while.  ( N.B. As mentioned previously, there are random differences in many of the puzzles --- sometimes even when you replay them yourself in the same 'game'.  This certainly applies to this puzzle!).
    About half way through the game (after you have traveled to the location where you have to exit a very rapidly closing door) there is a panel in which 12 symbols have to be 'frozen' (from left to right).  The process starts with the single left hand position which projects a continuous series of 12 symbols ending with one that is differentiated only by the fact that every time it appears you hear a sort of zither-ey sound.  (This "final symbol" is likely to be a different one of the 12 every time you play or replay the game!).  Let us call this symbol, X.  Then this same sequence repeats itself over and over again.  When you press the red button during the short period of time that any symbol is displayed, that particular symbol is frozen in place.  Then the 2nd position from the left repeats the same process (the zither-ey sound is always a signal that one series is ending and an identical one is about to start) ... and then the 3rd position; and so on.  You continue this process until all the 12 sites are filled with symbols.  Only if you have got all 12 "correct" have you solved the puzzle and continue to the next stage of the game --- if you make one single mistake you start the whole process again from the very beginning, which is pretty time consuming and frustrating!
    But what is the correct sequence of 12 symbols?  Opposite the cannon (earlier on) is a similar panel which projects one single symbol each time you press a red button.  It remains on screen for about 3 seconds and (unless you have a phenomenal memory) I can't think of any alternative but to make a rough sketch of each of the 12 symbols and in their correct order (or maybe use some lettering system??).  The order is different from the abovementioned one!  Since it's quite likely that you won't have time to make 12 adequate sketches first go, you can repeat this process as many times as you need to.  In fact it's worth repeating in any case since you'll notice an interesting and vital phenomenon --- there are only 11 different symbols here and one of the 12 symbols (always a different one, but always one of the 11) is always repeated but in the same 'position'.  Since I personally found this somewhat puzzling, I'll make it a bit clearer :- (Although your sequence might be different, I'm pretty sure that the same principle applies).
    In one particular case, calling the 12 symbols (opposite the cannon) A thro' L,  I found that the sequence A ---> L was identical every time except for E.  The first 'time round', E was the same symbol as G; the next time it was the same symbol as J; the next time, D; and so on.
    Returning to the 'original' puzzle panel :- The (ONLY) correct sequence you must 'freeze' here (from left to right) is the abovementioned ("near cannon sequence") A thro' L, EXCEPT that when you get to E (or whatever in your case) you must instead freeze the 'special' symbol X mentioned above.
    Hope it's clear ........... Simple if you know what you're doing --- almost impossible if you don't ---- one false move out of the 12 and I recommend that you start from the beginning again (or you'll waste a lot of time!!).

(9).    There is one puzzle which is very easy and obvious ---- what is possibly a bit less obvious is that one aspect of it is necessary for a later (albeit even easier) puzzle.

Puzzle {a} :-   This is only a slightly more complicated variation on the familiar "pairs/memory" puzzle.  You are presented with an 8 x 6 matrix of tiles.  I suggest drawing a grid of 8 columns and 6 rows.  As you click on the visible blank back of any tile, it flips over and reveals a symbol.  Sometimes (near the beginning) you are lucky and when you click again you get the same symbol, but generally not and the two flip back again ---- this, however, is of negligible importance.  In whichever way you prefer, you have to identify every one of the 48 symbols (which doesn't take long).  On your grid, mark each symbol (I found it quickest and easiest to call one which looked like a mustache M, a radio R, a fire-hydrant F, a skull S, and so on).  When you have done this, it is important to count (and note) all your M's, R's, F's, S's etc.  Each of the many times I have played this game, I personally got 10 sets of the identical symbols (maybe different in your case);  but each time, the positions and numbers of symbols in each set was quite different.  I  imagine that the only certainties are that each set must be an even number, and that the total must be 48.
    You then start again from the beginning with any symbol you like (say R) but you MUST then 'pair' it with a second R.  You then choose any other symbol (say S -- or preferably R if there are any left), and so on until the end.  Again, ONE slip up (i.e. an 'un-paired couple') and you start again from the very beginning (but the symbols remain identical and in their same positions, so it's not too time consuming!).

Puzzle {b} :-   Later, you come across a panel with only 3 out of the 10 (or whatever) of the same symbols that you found in Puzzle {a}.  Next to each of these 3 symbols is a sort of dice set to 1 pip.  By clicking on the red up-arrows below these 'dice' you simply increment each of the 3 (down-arrows decrement the pips) to the number of tiles in Puzzle {a} which had that particular symbol --- which is an additional good reason why you had to count and retain each set in Puzzle {a}.  You then click the circular yellow button above, and that's it .......... VERY easy!

(10).  When you reach the end of the game (or almost) you should have 20 video cassettes in your video cassette player.  However, each  time I've played the game I've missed one ... there could be more than one missing!
    It would be very convenient if the empty space(s) in your cassette player simply 'directed you to' the particular cassette(s) missing :- e.g. (Theoretically only) ... It would be nice if you were to know that IF (say) you find that the 9th slot from the left is empty, this would definitely mean that you have not acquired the specific cassette (say) 'beneath the radio'!
    Unfortunately however,  it does not seem possible to compile a simple list relating the positions of the 20 cassette slots on the video cassette player to the locations where the cassettes are to be found.  It appears that there is some built-in random factor at work, coupled with the particular but different order in which each person picks up the cassettes.
    It seems that the best that can be done is to list the locations in which all 20 cassettes are situated.  If you are missing one (or more), with luck this list may remind you of a location where you did not pick up a cassette.  Failing this, you just have to visit the locations listed below until you find your missing cassette(s).  The following list is roughly in the order of locations in which the cassettes will generally be encountered!

    {A}   Across the (first, green) bridge :-   In the room with the TNT figure.
           In the "Hall of Records" (Library) :-
    {B}    Just inside the entrance.
    {C}    After the slider puzzle, in the adjoining room.
    {D}    To the right; switch on the light; to the right again; open the spines; down the elevator.
    {E}    At the very end of the extremely long hall!
           In the "Water spitting, musical pipes" cottage :-
    {F}    In the first room you enter, beneath the TV set.
    {G}    In the adjacent room, one screen to the right of this.
    {H}    Up the 'spine ladder' and into the upper floor.
         After draining the lake; descending the stairs;  in the (yellow) house with the antenna and radio :-
    {I}    Just inside the house itself, below the radio.
    {J}   After turning into mini-Klayman; and then back again to normal, in the room with blue striped pillars and statues.
    {K}   After obtaining and climbing the ladder, in the upper room.
           In the "Second World" (that you enter through the door that closes VERY quickly!) :-
    {L} & {M}    (2 cassettes) In the purple room, before you exit the rapidly closing brown door.
    {N}    In the light brown house with the darker brown front door; down through the hole in the floor; in the dark room below.
    {O}    After solving the "12 symbols" puzzle; the door in the wall opened; in the orange colored room (with bars).
    {P}    In the light brown house with the purple door;  right, past the mouse and near the "pairs/memory" puzzle.
    {Q} & {R}    (2 cassettes) Back and left; past the entrance door and the "mouse/cheese" puzzle;  to the next room with the projector.
           In and around Klog's house :-
    {S}    Up in the red elevator to the next floor; in the purple room between the transporter and the cassette player.
    {T}    Inside the room with the dark purple door (with the projector and the mouse).

(11).    Caution:-  Be rather careful in acquiring the 3rd ('free') key near the end.
         Explanation :-  When you have got all 20 video cassettes, you 'receive' this key automatically.
    I made a bit of a mess of this!  I would advise saving BEFORE you pop the 20th cassette into any video cassette machine.  If everything is OK, when you insert the last cassette(s), all 20 cassettes automatically flash on and off continuously ----- previously, only the extreme left hand cassette lights up automatically unless you click another, and then you have to click the trigger above to start any batch off.
    In this 'final' case however, Willie Trombone then automatically relates the whole story from the beginning through to the end with no interruptions.  You MUST wait right through until he finishes ..... after the end, he then adds an additional short spiel and throws the 3rd key out of the video screen and at you, and you simply pick it up from the floor below the video set.
    Since I had heard many different segments of the story so many times during the course of the game, I didn't have the patience to listen yet again to the whole thing (which takes over 6 minutes) from start to finish!  So as far as I can remember, I guess I must have stopped him in mid stream.  After that, although all 20 cassettes were present, I didn't receive that final speech, and the key was not always available on the floor, and sometimes I couldn't finish the game without returning to a previous 'Save'.
    SO (I repeat) SAVE just before inserting that last cassette!!

GameBoomers Walkthroughs and Solutions