When you start Max OS X Leopard, the Setup Assistant appears. After filling it out and clicking Done, it still remains on your screen and won’t go away. Attempts to Force Quit the application doesn’t work either.

To solve this issue, you will need to restart your Mac in Safe Mode by holding down the Shift key while it starts.  Once you are in under Safe Mode, go to the Setup Assistant menu and quit.

Restart the computer and it shouldn’t bother you anymore.