Have you tried rebooting your computer? or have you actually run the unistall routine not just removed the shortcut? or god forbid just deleted the Magix directory (folder) from your hard drive leaving the settings in your registry unaffected?
I don't know how computer literate you are, would you know how to go into 'Windows Explorer' to check if the Magix directory is there or not because if you have just removed the 'Shortcuts' the directory will still be there and the 'Uninstall' routine should still work.
Just thought, probably the easiest solution would be to reinstall the download version then uninstall via 'Control Panel' reboot and then try installing the Pro 17 plus version again.
I've probably now done all 3 to be honest. Do you know how to check the registry file?