Multiple Accounts for Outlook 98 in Windows 2000 Pro

I have a machine running W2K Pro. There are 3 seperate user accounts set up on the computer, each needed to access e-mail. My problem is: All 3 users are receiving messages in Outlook from each others accounts. I tried creating seperate pst files, but Outlook said it couldn’t find them, what is going on??? I have setup computers like this before without this problem!
Thanks,
Tonda