Free Antivirus for Windows XP and Vista

Here is a list of some free antivirus softwares

Avast! Home Edition:

* Complete features with free for use for home users and non commercial users.
* Simple user interface and automatic updates

ClamWin

* Supports windows 98/Me/2000/XP and 2003.
* High detection rates for viruses and spyware.
* Can be used along with Microsoft Outlook to detect virus-infected attachments automatically.

Avira AntiVir:

* The free version protects against viruses, worms and Trojans, expensive dialers and phishing.
* AntiVir also provides free support.

AVG by GriSoft.com

*Fairly good antivirus system with an easy to understand interface.