Sounds like you might be infected with viruses or a candidate for a fresh install of Windows. If you need help with virus removal, follow the steps in this link and create a post in the Security Center
I have run Malwarebytes in full mode. It did find 6 problems on first sweep but nothing on following sweeps. Virus scan is negative; no problems.First off - if you have an 80GB hard drive - it's quite old, and I wouldn't be surprised if it was failing. Get a copy of Seatools for DOS and run it from the CD.
SeaTools | Seagate
If you haven't run Malwarebytes AntiMalware in Safe Mode, that would be my strong recommendation next.
I'll get one of these is right on the money.