It's probably spyware, I had a same type of problem. Either run adaware 6.0 and try to scan your PC or just go and edit your registry and search for one of the URLs that are popping up on you, once you find it, delete all occurrences in the registry.
BTW do this ONLY if you know how to manage your registry or you will screw up your windows more than it already is. Another solution is FORMAT C:
