Question: What antivirus software is out there that is compatable with Vista?

I just spent the last 6 hours trying to fix my husbands computer. Here are the details.

Vista computer, running internet explorer, outlook express mail and up to an hour ago McAfee antivirus.

I kept going in circles trying to upgrade microsoft. McAfee wouldn't UPDATE. Seems there was missing components after a microsoft upgrade. Not sure if that is what caused it but my husband said the PROBLEM started with the upgrade back on the 13th of November. Numerous attempts to fix McAfee. Used their autofix. Messed up Vista. Tried their un-install. Still left parts of McAfee. Did an un-install using Remove programs and finally GOT rid of it all.

Totally updated Vista now but have no antivirus software. The computer seems to be working fine. Mail and internet works. Clock in gadgets works. Fingers crossed.

What antivirus software is out there that works with Vista? I don't MIND paying for something if I don't have to go through what I just did. (Please list freebies too as I don't mind upgrading after trying something out).

Thank youI use F-Secure (ranked in top 4) and I believe they have it for Vista. Go to www.F-secure.com They are running a special right now.
Personally (and many other members would agree) I prefer AVG antivirus.
A free of charge version is available from http://free.grisoft.com
I find it's LIGHT on resources, and is effective in catching and removing viruses too.Thank you. I will look into the two options provided.I've been using AVG as well and it works great for me!