Don't ask how it got in, the only thing I can think it can be was a windows update, although that does seem very unlikely. But I had 'blaster keywhatever' get into my laptop and run riot with the workings. It started witha warning from a 'security centre' gizmo that told me my credit card details were being copied and then said it would get rid of the malware if I paid so much money. I had heard of this one before. It is another scam but it plays havoc with your pc.
I tried to wipe it off, I even downloaded a package that said it would do it, but the virus programme blocked everything. So I ended up getting the recovery disc out to sort things. NO I DID NOT because I never bothered to make one. Done a bit of F8ing and eventually reconfigured the laptop back to how it was when it was new. Great got rid of it, not soo great got rid of everything else. Photos, music, favorites, every programe I had loaded on it. Now I have to start all over again. Lesson for everybody. Make that backup disc and keep it up to date. I am now going to have hours of fun getting it back to rights.