Rejailbreaking 4.12->4.12 Please Help!

[jpascone]

I have a 3G which was successfully running a jailbroke 4.2.1 (not 4.1.2). Well, I made a huge mistake I won't go in to any detail but it rendered the device useless. I am able to place it in to DFU mode but really don't know where to go from here. I am running a PC. Could someone please help me by mapping out the steps involved? I would really appreciate it.
Many Thanks,
JP

[iYeow]

You can just put your iPhone into recovery mode and restore to Ofw of 4.2.1 provided you don't have iPad bb.