Adaware
Free version is off to the right.

Spybot Search-and-Destroy
Another great prog to remove stuff. Comes with a resident protection agent for IE.

Make sure both programs are updated using the built-in update tools.

After running scans using both programs (which should remove most major issues) and a fully updated virus scan using whatever Antivirus program you have
- A good free one is avast if you don't have antivirus.

If you still have problems, then you need to try a HijackThis log (see below this line).

In the event you need HJT, here's how to do it:
Go and download it from here: http://www.whatthetech.com/hijackthis. Scroll about halfway down or so and click the button with the flashing green light to the left of it. Open the program (extract to desktop if it's in a Zip file) and click the Scan and Save log button. It will then do the scan, then launch Notepad with the log file.

DO NOT FIX ANYTHING YET

Some of what it finds is also legit stuff, like Adobe's PDF plugin or the Google toolbar for example. You can either save this log and send it over one of my IMs, or you can also post it here (Board's gone til I do my new one, use email for now) and I'll pick it up when I check the board and take a look at it. Note that you don't need to register on my board to post a log, but you can if you want. I will post the processes to kill, files/folders to delete, programs to uninstall through Add/remove programs, and what HijackThis should fix. Once it's all fixed, post back with a new log so I can make sure I got everything.

That's about it for now, will update if something changes