try updating your windows software using the Microsoft Windows Update site by downloading and installing some new critical updates..
the site, if you don't know, is
http://v4.windowsupdate.microsoft.com..
follow the prompts..
afterwhich, if you have a third-party antivirus program installed, update its virus definition list from their website..
reboot your PC to safe mode..
run a full system virus scan..
good luck..