WARNING: You WILL loose all data on your Samsung Omnia by upgrading the firmware, so ensure you perform a backup before proceeding, and you DO run the risk of rendering your handset unusable “bricked” in the event of a power failure (ensure your handset battery is at least 75% charged) or an operating system error. Upgrade HH1 to HH3 (Debranding)

Original HH1 Firmware (Vodafone Branded)
PDA: i900XXHH1\ACHH1
Phone: i900BUHG5
New HH3 Firmware (Unbranded)
PDA: i900DXHH3/DXHH3
Phone: i900DXHH3

Download
http://rapidshare.com/files/14117444…XHH3.part1.rar
http://rapidshare.com/files/14118071…XHH3.part2.rar

or
http://www.mediafire.com/download.php?xocswrevoyj

1. Install Microsoft ActiveSync and Restart Windows XP
2. Install Samsung Model Driver and Restart Windows XP
3. Connect the Omnia to the computer via USB Cable
4. Wait for ActiveSync status to change to “Connected”
5. Run the Updater – i900DXHH3.exe
6. Switch off the Omnia and wait at least 30 seconds
7. Switch on the Omnia – Update Software Detects Phone
8. Click the Start button on the update software
9. EBOOT, PDA, CSC, Updates will process
10. COM port will be found
11. Installation will continue
12. When finished, updater will say “Job Done” and the phone will reset
13. Phone will take a few minutes to boot up and will auto reset for preconfig settings
14. Done – your phone is now debranded and is using HH3 firmware

I upgraded again from HH3 to HJ1, Singapore firmware direct from Samsung’s website, and in order to do that I had to change my handsets preconfiguration to Singapore, which then resets the phone, in order for the updater to allow me to go ahead with the install.
You can change your phones preconfiguration by doing the following:

1. Press the dial key to the left of the optical pad to bring up the dialer
2. Using the keypad, type in: *#1546792*#
3. Select “Preconfiguration”
4. Enter the pass code: *#81230*#
5. Select “Singapore” and accept the default operator
6. Accept this and the device will hard reset