If it is "Internet Antivirus Pro" its a virus. My antivirus failed me once and I had a virus like that slip past the goalie- it mimics windows security in appearance but won't let you run anything, or it constantly interrupts you for a "scan". You'll have to restart in safe mode and take a look at your startup programs and disable it. After that, do a full virus scan and hope it didn't damage your system too badly. Your mileage may vary, my computer was compromised to the point where I needed a clean OS reinstall.