Review Among free anti-virus software offerings, I like Avast Home Edition and AVG Anti-Virus Free Edition.

Both offerings are absolutely free and are compatible to Microsoft Windows 7.

AVG used to be very fast in version 7.5.  However, since v.8, AVG is slowing down our test platform.
If AVG is chosen, disable/unselect the AVG toolbar during installation which may speed thing a little faster.

Avast is basically maintain free and fast.  The only downsize is that Avast requires registration.  Home user is required to visit Avast web site and obtain a license code for free.  This license code grant the home user one year free license for using the free edition.

In summary, Avast is better and faster.  Unless the end user don’t like to go extra step to obtain a free license from Avast, AVG will be a better choice.