Mapped network drive problem when VPN disconnected

I have a customer with Windows 2000 Server and Exchange 2000. They have several Windows XP laptops with mapped drives to a shared user folder on the main server (which is the domain controller).

These mapped drives work perfectly in the office, and slowly but ok via VPN.

The problem I’m facing is that when off-site, if the users do not have the VPN connected, when they try to open a locally stored file in Word / Excel the computer hangs for up to a minute whilst it tries to locate the mapped drive.

Does anyone know how I can fix this as it’s causing our users a lot of frustration.

Thanks in advance!