You might also check out:

It is a good multipurpose scanner. There is a 14 day trial with the interactive protection running, but you can update and use it as a passive scanner after that for free.

A-Squared. A free scanner that specialises in trojans and diallers.

Remember that you always have reformatting and reinstallation as a last option.

You might also get a copy of Hijack This! and save the log file and post it here. Don't do anything until someone has looked at it for you