It works!!
Mark:
I have just had success mapping a Mac folder to an XP drive as you suggested. When I was trying to do it last night - and failing - I was in a public wireless hot spot. Today, at home on my own wireless network, it works (beautifully!!).
I don't know anywhere near as much about IP, routers, etc., as I wish, but I have proven that the link between XP and the mapped folder routes through my wireless router (Airport); as I was copying a large file from one XP to the Mac I turned off Airport on my MBP and the transfer stopped. Turned Airport back on and the transfer resumed. Because of this, I assume that the router at the hot spot disallowed the connection. Or maybe it had something to do with the fact that the IP addresses for both the Mac and the VM were both on the same network at the hot spot (no routing invoked?).
Maybe if Parallels could be equiped with some sort of simple internal IP routing capability, this mapping of a Mac folder to an Windows drive would not require a connection to any kind of network, which would be great.
Anyway, Mark, thanks for the suggestion. I'm a happy camper (while at home, at least).
Brian Shaw