Timothy - are you able to share your install logs? Look for all log files starting with "Python" in your %TEMP% directory.

We definitely do not (and without an installer rewrite, cannot) support simultaneous per-user and per-machine installs of the same version.

If you're just looking for the latest version for your own use, you may prefer to get it from the Windows Store instead. That one is per-user, won't interfere with other installs, and will give you global "python/python3/pip/pip3/etc." commands.