CCleaner is going to miss a lot of things. If memory serves, there's a sticky message over on the virus and security forum that gives a list of free malware removal programs.
After you've run all of those, I'd strongly recommend an "anything but Internet Explorer or Internet Explorer based" browser policy. You have about three major choices on Windows... Doesn't really matter much which one you pick, just pick the one you like and use it instead of Internet Explorer. Your choices would be: Mozilla Firefox, Seamonkey, and Opera. Everything else is likely to be based on IE, thus subject to the same problems as IE. This should help keep the problem from coming back. It's not a guarantee, but it's the best you're going to get at the present time.
I also often recommend an "anything but Outlook or Outlook Express" email client policy as well. I'm not aware of any other email clients using any part of those two, so take your pick of the dozens of options out there. Just sort of an added bonus, unless you enjoy receiving large quantities of spam. In which case, carry on using Outlook or Outlook Express. May you be blessed with more ***** enlargement pill, prescription drug, and 419 scam solicitations than you could ever hope to read through in a lifetime.