We have a Brother MCF-9440CN. We just replaced the Drum, but the reset menu wouldn't come up (normally, when you replace the drum, you go into the menu, you can reset the Drum life).
We looked all over the net for a solution, but couldn't find one.
So, we called Brother (oh, brother), and spoke to some jack-wagon. Eventually, we spoke to someone else and found out that, if you hold down the 3&9 buttons for 2 seconds, the reset menu will come up. Then you can reset the Drum life. It may have also had the belt unit in there, I don't remember.
Just thought I'd post this... in case some one else runs into the issue down the road.