AVG Anti-Virus has everything you need in an anti-virus program: e-mail scanning to include e-mail attachments, boot scanning and auto updating of the virus definitions. It's inexpensive and makes only a minor impact on system performance. Versions of AVG are also available with firewall and anti-spyware tools.

Computer Geex is an authorized AVG reseller.  You can purchase the award-winning software directly from the link below - it's very easy to install.