If you are looking for a free Anti-Virus Product we can recommend and use AVAST! Anti-Virus.
While the software does try often to sell upgrades to you, you ignore this can stick with the standard Free Version and be adequately protected from online and email based viruses.
The software update status checker is a handy feature that can let you know when updates for most common software such as Adobe Acrobat Reader and others are available.
See: www.avast.com