I'm with Bert. I do not put Antivirus on any of my servers. I have too many legitimate programs that most antivirus programs would freak out at. In order to explain why AV software screams at perfectly legitimate programs, it will have to be earlier in the day and I can't have this much wine in me at the same time, but there are legitimate reasons.
I especially do not put AV on my Hyper-V hosts. Besides, why bother. My hyper-v hosts NEVER see the Internet, and besides a baseline installation of Windows Server 2008 R2, they are just servers with 4 or 5 gigantic files on their drives (the vhd files of the guests).
JamesNT