OK, here're a few things I would do to.
1. I would log off and start Windows in Safe mode + Networking
2. Run regedit and check for strange things in:
HKLM > Software > Microsoft > Windows > Current Version > Run
HKLU > Software > Microsoft > Windows > Current Version > Run
3. Check C:\WINNT\win.ini for a [load] or run=something. If I see something like that pointing to a suspicious .exe I remove the line and try to delete the file
4. Go to C:\WINNT\system32\ and sort the files by date (newest on top) and delete all strange .exes and similar (things like asdzx123.exe usually)
5. Go to
http://www.definitivesolutions.com/bhodemon.htm and download BHODemon - tricky simple tool that cleans/blocks IE toolbars - much better than any spyware out there, when it comes to hidden IE toolbars.
6. Go to
http://www.pandasoftware.com/products/activescan.htm. On the right side you'll see "Free online virus scan". Use this to check your system, just in case.
If you think that you're ready to go, reboot the system in normal mode.
I hope this helps