Download and install http://www.filehippo.com/download_firefox/8900/ - Make default browser when prompted
In Firefox, 
Download and install http://www.filehippo.com/download_flashplayer_firefox/
Download and install http://www.filehippo.com/download_security_essentials_vista/
Restart if prompted, run Security Essentials and update virus database then perform a system scan