Microsoft Security Essentials is a free anti-virus program offered by Microsoft for users with GENUINE copies installed on their system (meaning that your copy of Windows must be legit and/or say "Genuine" in system properties.) I've read a few reviews on MSE and most of the reviews were positive; stating that Microsoft "hit the nail on the head" with this program. It is a basic anti-virus program that has everything to block out malware, spyware, virus, etc. but lacks a firewall (so you'll need to find a separate firewall program.) I have included a link below for the download if anyone is interested.