2 seperate harddrives and virus programs

I have two seperate hard drives each with there own
operating system. When I boot up I get the choice of
Other Windows Program (winXP sp3) or the Windows 7
(beta).

Do I need 2 seperate virus programs and firewalls, one
on each harddrive? When I go to windows explorer, I can
see the C drive and the F drive.

I have file andf printer sharing shut off on both drives
and I guess I would not rather use it. My computer is on
a home network with a wireless linksys router.
Presently have AVG Internet Security installed on my C
drive and windows 7 firewall turned on on the F drive.

Thanks

BD