Error: Message :
1. Exchange Servers placed in a OU which has GPO applied to them.
2. PowerShell Execution Policy set to unrestricted or remote signed.
Step1: Create a separate Organizational Unit in Active Directory and place Exchange Servers in that Organizational Unit . Do not apply any GPO on newly created Organizational Unit.
Step2: Log on to Exchange Server. Start Menu>Run>gpedit.msc
Right click on Local Computer Policy>Property>Disable computer Configuration settings and User Configuration Settings
Step3: Open PowerShell> issue the following command
Set-ExecutionPolicy –Scope LocalMachine –ExecutionPolicy Undefined –Confirm –Force
Step4: Reboot Server. Once rebooted log back on to the Exchange Server. check execution policy by issuing the command
Step5: Start Menu>Run>services.msc . Stop any backup software and Antispam software services on the server.
Step6: Upgrade HT/CAS Server: Download Exchange 2010 SP2 and install Exchange SP2 by the issuing the following command in PowerShell
Setup.com /M:Upgrade /InstallWindowsComponents
Apply Service Pack 2 to HT and MBX server first. If you have multiple servers in HT/CAS Array than you can apply service to one exchange array member. your exchange infrastructure still be functional and service mail systems.
Step7: download Update Rollup1 for Exchange 2010 SP2 and apply rollup1.
Step7: Upgrade Mailbox Server: Log on to MBX server. Open Exchange Management Console>Click Server Configuration>Select Mailbox>Select Server>Click Switchover Server>Browse and Select a server>click ok. Wait few minutes to finish the operation. Check the mailbox node again. It should show Is Active: False.
Now follow the previous steps to upgrade to SP2 and Rollup1.
Caution: Take a snapshot if Exchange is a virtual server. If exchange 2010 SP2 installation fails for another reason revert the snapshot back to original. Exchange will still be functional even active directory schema is upgraded by exchange SP2 installer.
If server is physical than the following URL might be handy for you.