Run adaware, spybot search and destroy (both available from www.download.com) and then run the microsoft anti spyware program.

After all that, click start, then run, then type msconfig, click on the startup tab, and untick anything you don't need to run at startup, click apply, then ok, then restart windows and see how it goes.

Also, run 2 virus scanners on the machine, just to be safe.

HTH