Recently my trial license expired, and after receiving our activation licenses, I needed to upgrade from the 'User' version to the 'Admin' version.
When uninstalling the previous 'User' version, it appeared to complete successfully, and I then started installing the 'Admin' version from the installer.
After installation completed, I noticed that three versions of Alteryx appeared in my Windows 'Programs and Features' in Control Panel - Alteryx (Remove Only), Alteryx (Admin), and Alteryx (User).
When attempting to uninstall the 'User' version, it appeared to complete as expected, but did nothing when examining the application or root directory location, and I could still access and open and use the 'User' version of Alteryx.
To make a long story short, after going into regedit and removing all registry keys named 'Alteryx' including the SRC source key for Alteryx, I was able to manually remove all three of these versions and reinstall the 'Admin' application successfully.
Some kind of an uninstaller to wipe out all Alteryx directories, installations/versions, etc. to perform a clean uninstall/reinstall would be super valuable and probably save some folks a ton of time who are evaluating the product and moving from a Trial(User) version to an activated Admin license.