Found this on the Microsoft Web site XADM: Do Not Back Up or Scan Exchange 2000 Drive M The information in this article applies to: Microsoft Exchange 2000 Server Summary Do not attempt to back up or use an antivirus scanner against drive M of an Exchange 2000 Server computer. If you do so, problems may occur with calendaring, access to attachments and messages, and damage to the Exchange 2000 database. Mail flow issues may also occur. For additional information about the latest service pack for Microsoft Exchange 2000 Server, click the article number below to view the article in the Microsoft Knowledge Base: Q301378 XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack More Information Only back up Exchange 2000 Server with an Exchange 2000-aware agent and only run Exchange 2000-aware antivirus programs. In addition, do not scan the files in the following folder: %SystemRoot%\System32\Inetsrv NOTE: Do not scan the EXCHSRVR directories. For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base: Q258243 XADM: How to Back Up and Restore an Exchange 2000 Server Computer Q271465 XADM: Clients Cannot Access Attachments After You Back Up Drive M Q285667 XADM: Understanding AV API2.0 in Exchange 2000 SP1