Microsoft Exchange – problem

I got my Exchange server running on a DC crashed. I had to Install the OS (Windows 2000 Adv Server) and Install Exchange Server 2000 on it again. Its also a DC.

The problem is that the users in AD still point to the old exchange server (the crashed one) and I can’t make new mail boxes for them, and exchange Tasks action just shows instant messging. If I create new user i can create a mail box however, I want to create mail boxes for the user that existed in the AD, (replicated from a member DC, when i ran dcpromo on this server). So any help would of great importance for me. Thanks