Q: I have spyware on my Mac what can I do????

I can't do anything with out getting a pop up.  I get pop ups telling me to call some 800 Microsoft number.  I have downloaded an update to my video player and an youtube mp3 converter (I'm thinking this was the money maker).  I've tried to delete history and cookies, but the pop ups still are pouring in.  I have checked my pop up blockers and every thing is how it should be.  Please help me figure out what to download so I can get ride of what ever my computer is infected with.  I don't know what to trust as I get pop ups every page I go to.