This will restore to T-Mobile 2.3.6 ULKL1.
This guide is for those who screwed up a flash, need to return their phone, are selling their phone, or just want that stock new phone feeling again.
2) USB Drivers
If you need your data backed up first, backup personal data with Kies and Application Data with Titanium Backup.
1) Download THIS file and extract it. (Password is 'sampro.pl') --Source HERE.
2) Power off your phone and remove the battery. Re-insert the battery after a few seconds.
3) Plug the USB cable into your computer, without plugging it into your phone.
4) Hold VOL UP + VOL DOWN while plugging in the USB cable to your phone. Stop holding with 'Warning' appears.
5) Press Volume UP and start ODIN (Run as Admin on Vista and 7, just to be safe)
6) Click PDA and locate the MD5 file extracted earlier.
7) Press 'Start' and be patient. It will take a few minutes because it is a large file.
8) Unplug your phone after it has completed and rebooted twice.
Now everything is 100% stock! Kernel, System, Bootloader, and Modem are stock.
If you're going to sell the phone, or just return it, I advise you to do the following:
1) Go to Settings > Privacy > Factory Data Reset
2) Check Format USB Storage
3) Press 'Reset Phone'
4) Press 'Erase Everything'
This will erase EVERYTHING on your phone including your SD Card (External + Internal)
If you happen to have a bootloop, perform the following:
1) Boot into recovery (Power on phone while holding VOL UP and VOL DOWN)
2) Wipe Data, Cache, and Dalvik
3) Reboot System
If this helped you save your phone, please press 'Thanks'
And if you want to, DONATE (You aren't required to, it's just HIGHLY appreciated.)