Can you run vista games on xp

Although it depends mostly on the game itself, for the most part, it's a no. For example, on Halo 3 for PC, it is Vista-only. Does it work on XP? No. This is because Vista is Microsoft's first operating system in which Microsoft completely rewrote the code from Windows XP (hence the long wait for the release). This makes it more secure, but as a result, it also it presents a whole new set of problems and compatibiility issues with Windows XP. Ironically however, running and XP game for Vista usually works, just right-click on the installer program and go to Properties>Compatibility. And then just change the "Run this program in compatibility mode for:" to Windows XP SP2.
It really does depend more on the game... the answer should be 'It depends' not a yes or a no. There are several websites on how to run the vista games on xp, and I actually have all but one of my vista 64 home prem. games on my XP SP3 .. But at the same time, I have a ton of old games (xp & older, and only two of them did work on vista)..
These two btw, were the two oldest games I have, one is even from Windows 3.1 and the other was obtained during Win95. So it depends. In some cases in past, all I had to do was add vb*.dll's to the proper location and games would run...I havent tried that with Vista since most are failing per my being 64bit.
Also doing the compatibility thing can work on some, but not on others. So again, it depends, try it, and do copy relievant files as needed..