What operating system are those who have played this demo using? XP, Vista or Windows 7? I have tried it on windows 7 (will install but not run) and windows XP (will install, and run with choppy sound, I created a savepoint, which saved, and then when I chose to exit the game it crashed the computer).

According to Steam -

• OS: Microsoft Windows XP SP2, Vista SP1 or 7
• Processor: Intel/AMD 2.0GHZ equivalent, or higher
• Memory: 1GB (XP)/2GB (Vista/7)
• Hard Disk Space: 8GB
• Video Card: : 256 MB 100% DirectX 9 compatible, ATI Radeon X800/Intel GMA 3000/Nvidia
• GeForce 6800 or Higher*
• DirectX®: 9.0
• Sound: DirectX 9 compatible

Thanks InlandAZ, I did check those already and I think I have or exceed those minimum requirements:

My computer specs are:
os Windows 7 professional
64 bit os
processor Intel core i7 CPU 2.67GHz
memory 6GB RAM
hard disc space 1TB
video card nvidea GTS240
directX 9.0
sound creative SB X-fi
(the computer is an alienware aurora PC just over a year old.)

The game installs then when I try to run it I get the error 'the next big thing has stopped working'.

If it's crashing under XP and Windows 7 you may have a corrupt download. Have you tried downloading the demo again?

Yes, I have tried each of the three download links, some of which for both the XP computer and my windows 7 computer, I thought the same thing. To be honest I don't think I can be bothered to try any more, life's too short. Thanks for trying to help, I am going to leave that game well alone now.