My latest annoyance was more and more laptops being hit with the following error whilst trying to install or remove software:

The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installed. Contact your support personnel for assistance.

After hours of investigating, unregistering dlls, reregistering dlls and trying to reinstall system files such as msiexec, it turns out Microsoft broke it with one of their updates.

On the 15th March 2016, MS released an update to fix an unrelated issue (KB3137061) and a different but more related issue (KB3139923). The first update was to fix a problem on Windows 7 and Server 2008 R2 machines that would experience problems with proxy settings if multiple RDP sessions were active on the machine. The second an update to fix another bad update on Windows 7, Windows 8.1, Server 2008 R2 and Server 2012 R2 which broke the option to repair installs via an MSI file.

It appears update KB3139923 is the more likely culprit, but in 1/4 of my test machines I needed to also remove KB3137061 to fix the problem of “The Windows Installer Service could not be accessed”.

The fix is pretty straight forward, assuming you don’t need the update for the above reasons, simply uninstall it:

1. Go to Start and click control panel.
2. Then in control panel, click uninstall a program.
3. From the left hand side choose “View installed updates”.
4. Select “Update for Microsoft Windows (KB3139923)” and choose “Uninstall”.
5. Restart your computer after uninstalling and repeat the above for “Update for Microsoft Windows (KB3137061)”.

If this doesn’t fix your problem, or you don’t have that update installed, take a look at this post on HowToGeek which has some useful suggestions.

I assume Microsoft will eventually release another update to fix this issue, but given their track record at fixing things in the past, I wouldn’t expect it any time soon. If you’re running a WSUS server on a corporate network, my advice would be to disallow this update ASAP.