Ah, I see. Great link that Rover found ya! So AVG offers some kind of free, generic boot up disc image for you to burn and use for such emergencies.
Yeah, you definitely DO NOT need to reinstall Windows for something like this. It's normally kinda easy if you had your Windows install disc. You would just boot to a Command Prompt with it, 'cd' to the system32/drivers folder and do something with those "avg*.sys" files, remove, rename, etc., then reboot normally off the hard-drive.
I've had this happen a few times myself.