Renpy the underlying program that runs these avn games, will work fine on any 32 bit operating system. Ie Windows XP, all 32 bit versions of Windows 7.
If renpy doesn't want to run under windows xp, then your going to have to run it under compatibility mode. Right click the 32 bit application in which ever avn game you want to play and then properties and go from there. I have been told it works great under windows 7 ultimate 32 bit so it should work great under windows xp. hope it helps! good luck