If you're having trouble getting the demo running, please review the system requirements:
System Requirements

The minimum system requirements are as follows:

COMPUTER: IBM PC or 100% compatible
OPERATING SYSTEM: Microsoft™ Windows 98SE/2000/XP (95/NT not supported)
CPU: Intel Pentium® 4 1.3 GHz (or AMD Athlon ™ equivalent)
RAM: 256Mb
GRAPHICS: 100% DirectX 9.0 compatible 32 MB * (see below for support cards)
SOUND: Windows 98SE/2000/XP compatible Sound card (100% DirectX 9.x compatible)
CD-ROM: Quad-speed (4x) CD-ROM drive
HARD DRIVE: 2GB free disk space
INPUT DEVICES: 100% Windows 98SE/2000/XP mouse and keyboard


The recommended system requirements are as follows:

CPU: Intel Pentium® 4 1.5Ghz (or AMD Athlon™ equivalent)
RAM: 512 MB
GRAPHICS: 100% DirectX® 9.0 compatible 3D Card w/ 64 MB
SOUND: Windows 98SE/2000/XP compatible Sound card (100% DirectX® 9.x compatible)
CD-ROM: Eight-speed (8x) CD-ROM drive or faster.
HARD DRIVE: 2GB free disk space

* Supported Chipsets – nVidia GeForce 3Ti/4Ti/Fx (MX series not supported). Radeon 8500/9XXX or higher. (Pixel/Vertex shader required)
If your system does not meet the minimum requirements, especially for video and sound cards, the game will not run on your system.

I will be pruning/locking threads which ask questions answered by referring to the sytem requirements.