You can scan a machine whose drive you can see via file and printer
sharing--i.e. scan the network-shared drive. You could do this across a
hostile medium by using a VPN connection.
I'm not clear how effective this kind of scanning would be in terms of
cleaning--I haven't seen any discussion of this. On a LAN, with
administrator permissions on the remote machine, this might work, but I'm
skeptical.
You can scan any visible (shared) drive or folder on the
LAN as long as you have Admin Access. However, you'll
lose one important feature "Memory Scanning" on the
remote machine.
Best bet, install the AntiSPY application on the remote
system, set it to auto update, scan and clean (or
quarantine) on a schedule.