Need help sharing the Outlook calendar

I have 3 computers networked together (peer to peer). 2 of them are WinXP, 1 is Win2000. The WinXP computers have OfficeXP, while the 2000 computer has Office2000. The problem I'm having is trying to get them to see each other's outlook calendars and contact lists.

What I did is, I shared the directory that contains the outlook.pst file and mapped it as a drive letter on the other machines. Then I've added the data file to outlook. At which point, I added the outlook shortcut bar links to the external calendars and contact lists. I've been able to get this to work. for a while at least.

The problem is, and I'm not sure what's exactly happening, but when they turn the computers off, or they leave them to sit for awhile or *something* else, they new shortcut bar links end up no longer pointing to the other computer, but to itself. Basically, I end up with 2 links to the same calendar and 2 links to the same contacts list. This happens on all 3 computers.

I'm pretty sure this would work just fine if they had an Exchange server, but that's a bit overkill for a 3 person company.

Any ideas?