Sounds like MS is hiring bottom of the barrel, if they gave you that advice. o.O

Only reason I can think of that would make me think that was a valid piece of advice is that he may have thought the problem was with your ISP. If he thought that after you told him/her all about the resource eating problem, it just goes to show the person didn't know much.

First thing I'd do is read up on Hijackthis in the Security forums, (there's a sticky topic right up top that'll tell you how to use Hijackthis, and post a log in a new thread in the Security forum, just so we can see if there's any spyware/adware/malware issues.

Second: After you've done that and been pronounced 'clean', I'd then look into things that could cause SP2 to act oddly. If you look at the top of this forum, you'll see a sticky topic about SP2, where I posted a fix for DiVX. The fix you can find in that message seems to work for a good many other SP2 problems, so you can try that fix. (I'd wait until after you've been pronounced clean though!).

Failing these, uninstalling SP2 for the moment could be your best bet, unless you're tough and want to keep chugging away at it, (I get like that heheh).

Luck to you.