I find the Official Atari TDU forums the best place for tech help, as they always have computer boffins online, and have lots of people (especially the mods) who know what they're talking about.
But please don't hesitate to post here as we will be glad to help.
If people don't wish to download the software listed, as I know I wouldn't, you can always just post your DxDiag file here and we can find out what is the problem or what gismos and gadgets you have ;).
For Windows XP...
1. Click on 'Start' Menu
2. Click 'Run'
3. Type 'DxDiag'
4. Save to computer
5. Upload on here via managements.
Minimum Specs for TDU:
Operating System : Windows 2000/XP/Vista
CPU : Intel P4 @ 2.4Ghz or AMD Athlon 2800+.
GPU (Video Cards) : ATI Radeon 9800 256MB VRAM or Nvidia 6600 GT with 256 MB of VRAM.
Video Cards with vertex/pixel shaders 2.x and above are recommended.
SPU (Sound Cards) : DirectX 9.0 compatible Sound Card.
System Memory : 512 MB, 1 GB recommended
Hard Disk free space: 8 GB
DVD drive: 8x minimum
DirectX 9.0C (included)