Mapped drives on a workgroup?

I help out with a local womens shelter at their office. They have a
workgroup network with a windows 2003 server based server (enterprise
edition).

Anyhow, most of the pcs are XP, but we got a new one in this week with
Vista Home Premium. When I map network drives everything is fine until
we reboot or log off. We get a message "vista could not reconnect
network drives" and sure enough, I have to type in the admin username
and passworrd to connect them again.

What is going on and can this be fixed? This seems such a simple
task.

chaz