Had a customer that needed their older version of Office Pro Plus 2010 reinstalled. During the installation I got the following error.

The error lead me to the following Microsoft support page.

https://support.microsoft.com/en-us/help/2642495/the-windows-installer-service-could-not-be-accessed-error-when-you-try

I used Method 1 and was successful. Make sure to include the following line at the top of the Registry entry.

Windows Registry Editor Version 5.00

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