Vista and XP Game Share?

Ok guys this may sound like an odd question but is it possible to have Windows Vista and XP share game files? My current system has a triple boot of Windows XP and Vista as well as Ubuntu. I want to try and save hard drive space (those are in partitions not seperate hard drives) because for general use I've been using Vista but when I play a DX9 game (the majority) I'll switch over to XP. But in some cases where a game is both DX9 and DX10 compliant I like to switch to XP for MP games to keep my FPS with DX9 but as you can see the expense to the hard drive is crazy (2 Crysis installations!). So I was wondering if maybe I made a shrink on some of the space and created a gaming partition, could I have both OS's able to access the files in some manner?

yes it would work if u install games on xp or vista and play on the other os. Sometimes when u click on the game .exe on the other OS an error will come up saying d3dx10.dll (the exact .dll file will be different.) To overcome this problem u got into the X:\Windows\system32\(game .dlls are usually stored there) folder of the os u installed the game and copy it to the other os. Most games will work, rarely one in 10 games wont.

I can verify that it is no problem. I had lots of games installed XP and installed a dual boot Vista (both 64bit). To play my games on Vista all I needed to do was install updates, service pack one, and directx 9. To get my save games to work I had to copy the files from docs and settings/user folder for xp to the user folder in vista. So basically install updates, directx 9 and make shortcuts to your game executables. No need to install game twice or play with the registry.

Only game I tried that didn't work right doing this was Gears of War, and I think it had something to do with Windows Live, but I don't remember.

XP is better for games anyway, so just play the games when you are booted with XP, and Vista for whatever else you want to do.