Hi, I use Spybot, Adaware, AVG, & Zonealarm which are all very good and free.
If you can't get rid of it, boot into safe mode [ press f8 repeately whilst starting up] either try to save any important info to disc media and download " system mechanic" in think it still has a 30 day fre trial [ fully functional ] and that has a great program for deleting crap, if your running XP try system restore, may be able to go back to another day when i was clean, if that works then run all anti virus programs, if all thats no chop well just reinstal your OS agian.
goog luck
Brian