When using a PC as a NVR or DVR, what virus protection software do you guys use? Does client pay subscription?

symantec corporate edition...never expires

Lock down the PC then you wont need any.

We are in a corporate IT environment (BHPB). So by using an NVR, IT are oblivious to the use of the server. It just looks like an SQL server to them and they look after all service packs and virus scanning etc.

Be warned that any SQL is far more susceptible to virus's and hacking than a normal server. This is because it advertises its existence and there are powerful queries you can run to exploit the server if not properly secured.

We used Norton long ago... now only Sophos all around.

Personally, I do NOT like the idea of having a PC based DVR with a Public IP address (which means it is accessible to the Internet and not on a local private LAN only - or a local private IP which translates to a Public IP using NAT or whatever) w/o virus protection of some sort.

have you tried TCP/IP port filtering and stripping XP right down to barebones?
As that then stops most of the normal threats since there is nothing really for one to get into and use. A real hacker can bypass most AVs out there today and thats the only ones that would get into any of my PCs. Once you have that network cable plugged in, thats all that matters. ;)