I just installed Google Music Manager on Windows XP Pro.
Every time I turn on the PC, Music Manager is starting.
How can I uninstall Music Manager and stop this behavior?
You can use either of these two options to avoid running Musicmanager as you start the computer:
You could actually just open up the program normally (double click on the orange headphones in the system tray, for example), and click on the Advanced Tab
From there Uncheck the box next to "Start Automatically when computer is restarted". Then restart the computer, and Music Manager should not start automatically.
That should solve your problem.