First, when you say you ‘reverted’ to XP Pro, I will assume you did a complete uninstall/reinstall of ALL software. If not, start there.
After that, try trashing your Prefs file (second item in the FAQ folder) <
http://www.adobeforums.com/webx/.ef4a07f/0>
If that doesn’t do it, check your preferences in Adobe itself to see how much memory, etc. you are allowing it. Increase as necessary.
Beyond that, I’m just a minor wizard, junior grade. We’ll have to hope that one of the Yodas will help.