I had the same issue as well. I was looking at funny videos when i got whats called Malware. The virus essentially puts up false alarms that makes you go to there website to buy the software that is bogus. The thing is real deceptive and real difficult to get to the root of the virus.
The easiest way to remove this virus is to reinstall the Operating system, whether its XP or Windows 7.
see posts #34 and #50