WinXP Home, Office 2003, Outlook 2003

Two people working in a home office with a PC and a Laptop on a LAN
sharing the work files stored on the PC.
When working with Outlook on the laptop it normally points to the pst
file on the PC. We have learned that we can not use Outlook
simultaneously on both systems and also this is not convenient we seem
to get by.

All work files including the pst file are backed up to the Laptop once
a day.

In an emergency I would like to be able to disconnect the Laptop from
the LAN, open Outlook and open the backed up PST file on the Laptop.

However, whilst the Laptop is disconnected from the LAN I'm unable to
start Outlook and I get the following message:
"Unable to open the Outlook Window. The set of folders could not be
opened. The server is not available. Contact your administrator if
this condition persists."

Since Outlook does not open up I don't seem to have a chance to point
it to the backed up files.
Can someone help me please?

Chris