autoruns may find another startup location.
I also seem to remember an option someplace to restore last windows explorer windows upon restart. You'd need to close the window and shut down or log off cleanly. If you crash or otherwise don't shut down cleanly, it will keep re-opening windows explorer at every login by that user.
Just checked...in windows explorer, tool/Folder Options, select the View tab, scroll down to the checkbox for "Restore previous folder windows at logon" and make sure it's unchecked. Actually, do that first before bothering w/ autoruns.