Assuming you have visited all the porn sites and 4chan and have the ASK TOOLBAR installed.
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If not the above then I suspect because of the age of it you will need to take it apart and reapply thermal past to the cpu.
You are pretty lucky if that is the original hard drive that came with it.
I suggest running chkdsk on the ( c ) drive and do a virus scan then report back here with any updates.
Thanks,
Inachu