I don't recommend classmates.com as they spam the crap out of you.
Myspace is hit or miss. I haven't found too many people on it.
Spock is a new service that is beta only and I haven't found any purpose for it, but I have the beta. It is supposed to be a people search. www.spock.com
I've heard a lot of talk about ZabaSearch. It searches publicly able government records as well as some commercial sources. A lot of people say that it violates their privacy because it's so easy to find people, so I guess it works pretty good.
Probably overheating? Can you check your case for proper ventilation (fans running, good air flow so cables aren't getting in the way) or lots of dust?
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