I presently use Norton for my anti-virus, which is expiring soon.  I've read a lot of threads about poor performance with different types of ant-virus software, particularly Norton.  I'd like some comments on what type of anti-virus software guys are using, and any suggestions as to whether I should renew my Norton account or try another.

I run FSX Deluxe with Acceleration.  My OS is Vista Premium 64 bit.

Core 2 Quad (3.2GHz)
nVidia 8800 Ultra
4GB Ram

Don't know which to recomend.  I have McAfee, but that is because MSN gives it to me free.
I'll tell you what I do about it as it relates to performance though.  Most of my FS machines don't even go on the net, so they do not even have firewalls or anything. Any files get screened through the one machine I do allow on the net before I put the files on the other machines.
The on machine I do allow on, when I fly, it's completley disconnected from everything, so I can turn all the security off.  It's much easier than worrying about which AntiV will slow my machine the worst.

Trend Micro works great for me and runs fantastic with Vista. And there aren't annoying popups in the corner of your screen every 5 minutes.

Thanks for your comments.  I think I'll give AVG a try.