From what you've described I can say one thing with certainty: I have no idea what you were attempting to do or why.
Anyways there's no IOS257, I'll assume it's a typo. Only uninstalling your system IOS is going to cause a black screen (aka brick). I've moved your post to the bricked forum where someone will hopefully be able to help you out.
Try this: Boot the console with no disc/sd/memory card inserted and watch the disc light. 1 flash or 2?