At one site of a customer, where running Exchange Server 2003 on top of Windows Server 2003, faced a problem with the IIS manager. The MMC console doesn’t find it, you cannot add the snap-in because it’s not there. Removing/re-installting the IIS is not an option because the E2K3 is there.
I thought there must be some DLL registration missing, similar to the Schema Admin add-in, where you need to manually register the schmmgmt.dll file (run regsvr32 schmmgmt.dll). So keep searching till found the inetmgr.dll under the %windows%system32inetsrv folder.