HD boxes are a bitch for doing this, as above hold the back up button on the box, may take some time as they are lazy as fook. I dont know how many I had to replace coz of this.

If that doesnt do the trick and you are prepared to loose all your recordings, do the same process but hold the left and right arrows on the box, this will do a master reset of the box LAST RESORT THOUGH.

What make is your box mate? Samsung Pace or Thomson, will tell you on the back. I can advise you if you are out of warranty