...an illegal operation and will be shut down.

[Mobhack]

Some points to check:

1) Do you have DirectX 8.1 or better installed on your PC?

2) Is your "voodo" graphics card a 3D accelerator type card?.

Our playtesters have managed to play the game on the minimum specs as outlined on the shrapnel site:
* Pentium II 500 MHz
* 128 MB RAM
* Windows 95+
* Minimum 200 MB HDD Space
* 8X CD ROM
* DirectX 8.1
* 3D Accelerator with 32 MB RAM
* Windows Compatible Sound Card
* Mouse

I'd also consider doing a defrag of your hard drive, with a surface test for bad sectors as well, if you have not done that for a while. (It takes a lot of time with the bad sector test, so that would be an overnight job). Any bad sectors, or unlinked clusters on your drive can cause some weird errors.

Cheers
Andy