I had a similiar situation. Friend has a unit that we want to donate, recycle, or sell. I called MSN TV support at 1-800-469-3288. Here are the steps:
Had to have the unit hooked up but turned off.
Had to be sure there was not an active MSN TV account.
Had to have the keyboard.
Then I was told to:
Hit OPTIONS button (bottom row of keyboard) THREE times
Then enter 32768
Some lights flash on the unit.
Now supposedly (hopefully) your information is removed from the hard drive.
If you want to get the info straight from the horse's mouse, just call. I got through right away. And although they wanted to know phone number for the old account (that I did not know)-they took my current phone number instead, since they needed a way to log the call.