haywiresystems.com

we have cleaned “xp antivirus” off of numerous machines in the past several months. this is a nasty piece of malware –or virus if you ask me! the program tries to trick users into buying their antivirus program by virtually prohibiting internet browsing with pop-ups, blank home pages, and [...]

We have been using a couple of different FREE anti virus programs with different clients. The first is AVG Antivirus.
The second program is Clamwin antivirus. Clamwin is an open source program, accepting donations.
Both of these programs are “less heavy” than the larger companies products and both offer regular updates.