I had something like that late last year. Extremely annoying!! Do what Ryzza said as it will most likely work. Otherwise I guess you could try system restore if the program is quite new on your computer. That should kill it.
I remember the stupid one I had. It was called XP anti virus 2009 and it disabled all my internet, tried to get into mcafee which had all my account and bank info (thank god it didn't) and it made everything painfully slow. 10 minute start ups were all I could get. I had to re format the entire Hard Drive and obviously reinstall PC. But hopefully yours won't get to that stage. haha.
I don't really see what people get out of making huge Rogue viruses and Malware. Unless of course people are actually gullible to pay them $80 to buy a full version of a program that takes over your PC because you suddenly have 100 or so non-existent viruses. Hmm, I guess they must get bored.