When you say reversion, does that mean you did a simple reinstall of XP over Vista? Or perhaps did you do a full system wipe/reformat before reinstalling? It really seems like you may have done the first option, which is not necessarily a good idea. If you can, you might try backing up all your important data (docs, bookmarks, email, savegames, etcetc), reformatting your HDD, and then installing XP clean that way. I'm also going to assume that this is a machine you've had XP fully working on before, so drivers shouldn't be an issue for you.