I have this issue as well. I have an original Xbox that I purchased used. Problem is someone had put a failed soft-mod on it and not all the hard drive is available (the original dashboard works fine, thank goodness). I have looked all over the internet and contacted Microsoft twice to get my unique "code" to allow for the factory reset. Every code I have tried has not worked and it seems the only options are to
A. open the console up, hook the drive up to my PC and fix it that way.
B try every possible button combination.
C try to find the elusive factory reset disc.
Any information you guys might have would also be helpful!!