Windows Installer always says "Another program is being installed"

Solution 1:

Open regedit and see if this key exists:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\InProgress

If so, remove it. Restart the Windows Installer service after removing the key.

Solution 2:

Fire up Process Explorer and hover your mouse over each instance of msiexec.exe. With a bit of luck you'll get the command line of what's installing which should give you some clues as to what it is.

I get this from time to time and it's my antivirus installing something which I can only guess is new definitions, because it happens frequently enough for me to notice.

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Solution 3:

Sorry if this is a basic response...but, do you have any pending windows updates that need to have their installation finalized via a reboot?

On a side-note, using Windows Installer Cleanup Tool was the biggest mistake I ever made. Just thought I'd throw that in. ;)

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Solution 4:

First thing is to try stopping the Windows Installer Service. That may resolve the problem in itself. Quite possibly Windows is installing updates in the background.