According to an old post by
Mag, the save files for Rhem 4 should be located in:
C:\program files\RHEM4\Data\DPOT
or
C:\program files (x86)\RHEM4\Data\DPOT
if you're running the 64-bit version of Windows 7.
To get there:
1. Click Start (The round button in the bottom left of the screen with a Windows log on it) and then click "Computer".
2. Double-click the main hard drive (usually called "Local Disk (C:)", or possibly something else ending in (C:).)
3. Double-click "Program Files (x86)" if it's present, or else click "Program Files".
4. Double-click "RHEM4".
5. Double-click "Data"
6. Double-click "DPOT"
At that point you should be able to see your save files.
Make sure you copy them to another location on the hard drive as a backup (like a folder in My Documents) before you make any changes.