"Windows XP SP 2 on a Dell Dimension XPS T500 computer that has a Pentium III 498 MHZ processor and 640 MB RAM. I have a 3dfx Voodoo 3 16MB video card."

Sorry, but there is no cure here since this machine is about the point I've found DVD playback to start working on Windows 2000/XP. Maybe there are combinations of drivers or settings you can try but I found such to be an investment of time I can't afford. I hand out a shopping list of what to try and let the owner have at it.

-> Try a GEEXBOX bootcd from google.com since it will not have the overhead of windows.