my sister got a virus called System Tool on her laptop a while ago. she don't know how and where she got it, but the last thing she remember doing was downloading an email attachment. it was a 2011 virus, a fake anti-virus that turns your real anti-virus OFF! and then it will start taking over your computer. it runs a system scan that makes it look like a real anti-spyware program. and when you're fooled, it's going to offer you a service, i don't know if it's for real but i'm think it will filch money from you. so better be careful!
good thing, we were able to solve the problem right away :D

just in case you also got that virus, all you have to do is to restart your computer, run in safe mode (so the virus couldn't start automatically) and then do system restore. that's all.

but of course, prevention is better than cure :D so before opening emails from unidentified sender or installing/downloading unknown programs and files, always be sure that it is a hundred percent SAFE! it's always better to stop something bad from happening than to deal with it after it has happened :D