When you try to install a cumulative update for Microsoft Exchange, the Readiness Checker may fail and prevent you from continuing with the upgrade and installation. The following error or a similar error will be displayed:

“A restart from a previous installation is pending. Please restart the system, then run the installer again. For more information visit: http://technet.microsoft.com/library(EXCHG.150)/ms.exch.setupreadiness.RebootPending.asp”

The solution

First, I left the Exchange CU installer window open while checking the prerequisites.

• Open the registry editor
• Go to HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager
• Rename the key “PendingFileRenameOperations”
• Rerun the prerequisite check that you left open

Note: Export the registry key before making any changes and be careful when making any changes to the registry as it can cause serious problems if not handled properly.