I. Before You Begin
1. The only real reason to unroot a phone is to send it in for warranty, otherwise just flash a different custom ROM.
II. Format the SD card
1. On your phone go to Settings > SD Card and Phone Storage
2. Select Unmount SD Card
3. Then select Format SD card
III. Unroot the Phone
1. Download the latest firmware file for your device and the Original SPL and save it to your computer. (if anyone has other .nbh firmware files for Dreams from other countries please post links in the comments and we’ll add them to the post).
2. Plug your phone in via USB cable and mount the sd card so we can transfer files to it.
3. Copy the .nbh file and the SPL update.zip file to the root of the sd card (NOT in any folders, just on the sd card itself).
4. Unplug the phone.
5. Turn off the phone.
6. Turn the phone back on by holding down Home and Power (keep holding it until the recovery screen comes up)
7. In recovery mode we are going flash the update.zip to apply the SPL update.
8. Once it is done, the phone should reboot.
9. Turn off the phone.
10. Turn on the phone by holding down Camera and Power.
11. It should automatically recognize the .nbh file and ask you to push power to begin.
12. Once it is done, push the trackball to restart the phone.