did you know that 67% of PCs have spyware, and that the average Windows based PC is attacked with 2min of being online.
Perform a Spyware scan, and then perform a Virus Scan i usually reccommend Webroot Spysweeper and Mcafee VirusScan with Zonealarm free version. After you do all this, flush you system restore cache: Start-control Panel-Performance and Maintenence- choose "free up space on hard disk" then at tabs along the top click "more options" and then click clean up on system restore section.
WARNING!!: this will cause you to lose all you previous restore points, however many viruses and spyware reside on the system restore folder, so even if you scan and delete the virus, it can still reappear. So deleting the restore cache will delete all forms of this.
...AMD