Python 3.8.0 Setup Failed - 0x80070666 Another version of this product is already installed / No Python installation detected


I installed 3.8.7, the dependencies didn't match up with the project I was trying so I uninstalled 3.8.7 and wanted to try 3.8.0. I get this error every time.

Things I've tried:

  • Using Windows "Remove apps and programs". Doing this results in an error "No python 3.8 installation was found", an incredibly frustrating contradiction.
  • Trying everything from this thread, including removing environment variable paths, deleting registry \SOFTWARE\Python\PythonCore3.8 (it was only there for HKEY_CURRENT_USER and wasn't there for HKEY_LOCAL_MACHINE)
  • Tried uninstalling 3.8.7 with my 3.8.7 installation .exe, which brings up a "Modify Setup" screen (so it recognizes an installation somehow), but clicking uninstall brings up an error "No Python 3.8 installation was detected." I also tried the "Repair" option, which gives the same error. Choosing the "Modify" option shows me where another installation was (on my OS hard drive) that I deleted, and then ultimately going through with the modify process resulted in the same error as the other two options.

Every time I run a Python uninstallation it recreates the registry keys and the folders, but in the OS drive where none of my installations are. I can't direct the uninstallation program to uninstall from another path.

I'm thinking it's a combination of choosing my own installation paths (which is almost always never worth the trouble it causes) and the fact that my Python paths are not on my OS drive.

asked on Stack Overflow Feb 1, 2021 by jangles • edited Feb 1, 2021 by jangles

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