Be alert for these symptoms of viruses
How do I … know if my machine has a virus?
There’s no one test to answer that question. Three general patterns indicate your computer has been compromised.
• Odd slowing down or unusual hard drive activity when you’re not at the keyboard (obvious by the hard drive light on the console indicating files being changed).
• Reboots. When your machine unexpectedly decides it has to reboot, that’s not good. Viruses or Trojans do this sort of thing.
• Hijacked browser pages. If your Web browser’s start page is changed or can’t be changed, that’s another telltale indicator. First step in response: update your antivirus program immediately. Shut down, reboot and do a full system scan.