yo!
The XP is REALLY slow, because it's old....no?
This provides most all the methods for Windows 7:
http://www.sevenforums.com/tutorials/14 ... hange.html
The bits you want are methods 1, 2 and 3 - don't bother with the registry stuff unless you are happy you know what you are doing. Method 3 allows you to re-enable things if you find you are missing something.
AS for WHAT to disable.......lots of searching and some common sense (if you see a startup item called EPSON printer, you can assume it's a printer related thing - like a quick launch, etc - you can remove this).
BG