need to retain previous version of office alongside latest version

Question

I would like to retain ms office 2021 and reinstall ms365. Is that possible?

Answer 1

Usually, no. In most cases, Microsoft 365 and Office 2021 can’t run together on the same PC because both are typically Click-to-Run installations.

There are two important exceptions and caveats:

1. If one of the two products was installed through MSI deployment, they can run side-by-side.
2. If both are standard consumer/home installs, installing one usually removes or conflicts with the other.

For a home Windows setup, the supported expectation is:

• installing the newer Office product often removes the earlier version
• running both side-by-side is generally not supported

If the goal is to go back temporarily because of a problem in Microsoft 365, a supported option is to revert Microsoft 365 to an earlier version instead of keeping Office 2021 alongside it. Note: reverting reduces access to the latest security, performance, and reliability improvements, so the issue severity should be weighed first.

If an install attempt fails with an “another installation is in progress” type error, restart the PC and then reinstall Office.

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References:

• Install and use different versions of Office on the same PC
• How do I upgrade Office?
• How to revert to an earlier version of Office
• "...Another installation is in progress..." or error code 0-1018, 17003-2031, or 2035-0 when installing Office