I had similar problems after reinstalling LS, after upgrading to XP, since i was only running a system slightly above the minimum requirements, however, all of the programs loaded into my startup sequence was just hogging my system resourses and making my system stall.

Now, Maximum PC ran an article on "How to put Windows XP on a Diet", in thier Nov. or Dec. Issue, and it gave detailed directions to eliminate unneeded processes at startup, and programs that come with xp's initial install that you never use. You should see if you can find the issue, if not drop me a line, i'll see what i can do about getting a reprint.