Virtual PC - Firewall - Virus Protection

[grrr223]

I am looking for other's opinions on how to protect my Windows XP Virtual PC 6.1 installation.

I currently am using Virtual PC to connect to my company's VPN through "Shared Networking" and I was wondering what is actually necessary to protect Windows from the outside world.

Anti-virus
It looks like it makes sense to install virus software in Windows as any Mac anti-virus software wouldn't see any of those files.

Firewall
Does the Firewall in Panther protect my Virtual PC installation because I'm using Shared Networking? Would there be any benefit to using a firewall in Windows also? Are there any specific ports I need to open up to allow my vpn to continue to connect?

Thanks.