I had installed moi_v5_beta_May-22-2022_setup.exe, but the trial expired, so I tried to re-associate the 3dm extension with MoI v4.

Even when selecting C:\Program Files\MoI 4.0\MoI.exe from the reference, MoI v4 is not added to the list of programs to open the file. It always launches the expired v5 beta.

I then tried uninstalling v5 beta (May-22-2022), but just like before, MoI v4 is not added to the list of programs to open the file.

It seems that many users have installed the new beta, but is it possible to re-associate the extension with version 4? Do I need to edit the registry?

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MoI version4, windows7,
marzRX

Hi marzRX, you might try the control panel method for setting associations, the 2nd method mentioned here:
https://fileinfo.com/help/windows_7_file_associations

Another thing you can try is to uninstall v4 and then re-install it, the installer should set the file associations.

There is also a new v5 beta that you can get at https://moi3d.com/beta.htm .

If nothing else works then the place to set it in the registry is under:
  HKEY_CLASSES_ROOT\MoI.3DMFile.1\shell\open\command
which will have a value like this:

"C:\Program Files\MoI 5.0 beta Apr-8-2023\moi.exe" "%1"

You'd change that path to the v4 moi.exe

- Michael

Thank you, Michael. I was able to associate the extension by modifying the registry key as you suggested.

I chose to edit the registry key because I was worried that settings like CustomUI setup would be lost if I reinstalled v4.
(I had already tried both methods 1 and 2 before asking the question.)
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marzRX