Just found out the hard way that Exchange doesn’t like the removal of an AV product. Check out the link below for the easy fix.
Great job, Paul, and thank you!
Information Store won’t mount after removing Anti-Virus software
by Matthew Pusey on June 12, 2011
We all know Exchange doesn’t exactly Anti-Virus software and realtime scanning to begin with. However, it looks like in Exchange 2010, it doesn’t even like it when you remove it! There is a registry setting that needs to be manually changed or the Information won’t start and you’ll see a lot of this in your event logs:
The fix is in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\VirusScan
Make sure this value is set to 0(Zero) and then exit out of the registry. The information store service will now start.