In Exchange Server 2007, the responsibility of managing recipients moves backs to Exchange Server. Recipients are now managed using the Exchange Management Console (EMC) or the Exchange Management Shell (EMS or "the shell"). There are no extensions to Active Directory Users & Computers (ADUC) console, and no Exchange Tasks in ADUC either.
Though the initial reaction is that of annoyance ("..why does Microsoft want us to change the way we do things, just when we're getting so used to it?"), understanding some of the changes made under the hood and the resulting benefits derived from those may make one change one's mind about this issue.
Did you experience or otherwise hear about a lot of issues with Exchange attributes not being populated, recipients not being mailbox or mail-enabled in Exchange Server 2003/2000?
The Recipient Update Service (RUS), an Exchange Server 2003/2000 component that was the cause of a lot of support issues, has been all but removed. From an operations perspective, RUS, and the accompanying support issues, are history.
Using EMC/EMS, recipients get provisioned instantly. The shell also allows a lot more automation.
further you can install EMC only without any server roles on any machine and and manage your exchange 2007 server , ther are 32-bit and 64-bit available