The only possible advice: contact the seller and ask how to solve this.
I bought a cheap mp3 player on eBay (OK, I am a student and didn't have the money to buy a good one at the moment). I deleted the crap on it immediately (just a few crappy songs) and now it is dead!
I have found a couple of threads on the net started by people having the same problem (dead mp3 player after deleting factory songs), but there were no answers...
There is no reset button or hole.