How to unbrand/debrand your Sony Ericsson

To use flash menus and some other features of a generic phone one needs to debrand it.
A little explanation about the subject:
Original Sony Ericsson phones come with GENERIC firmware. When sold from an operator under subscription and similar, operator modifies the firmware (something like "phone's operating system") so that it's design and appearance match the operator's design. Such phones in most cases don't have flash menus enabled, and some don't even have Flash Player.
Unbranding is done by modifying phone's CDA to match one of GENERIC phone's so that Sony Ericsson Update Service would flash it with a generic firmware.

Video version: http://www.youtube.com/watch?v=z-jPvHyPldQ&fmt=22

Warning

Before starting this please use Sony Ericsson PC Suite to backup your contacts and messages.
After you unbrand your phone it will be like new with clean generic firmware. All applications, settings and contacts will be lost. If you back them up restoring is a breeze.
This totorial is for A2 phones ONLY! These are the phones available on the list of models in the program you will use.

Phase 1

The first thing you will need is "SE CDA File Maker", it's a small program created by ŦҢĄ ρяØאÌЙâťőЯ. It's latest version is no longer free. You can also still download the version 2.0 from the site which is free. Download it and unpack the .zip file.

1. Download the A2 CDA File Generator, it's in a ZIP file so extract it
2. Launch A2 CDA File Generator.exe file and the program will start.
3. On the list pick your phone model.
4. From the Region/Branding pick your region. Here is the list of languages per region for A2 phones (thanks to wrox):
   
   

   BALTIC:

   English, Estonian, Lithuanian, Latvian, Russian

   HONG_KONG:

   English, Chinese (in Hong Kong)

   NORDIC:

   English, Albanian, Arabic, Croatian, Danish, Finnish, (+ Icelandic), Norwegian, Swedish, Turkish

   WESTERN-EUROPE:

   English, Dutch, French, Portuguese, Spanish, Turkish, Polish

   ADRIATIC:

   English, Albanian, Bulgarian, Croatian, French, German, Greek, Italian, Romanian, Russian

   AMERICA:

   English for American, Portuguese for Brazil, French for Canada, Spanish for Latin American, Dutch, French, Spanish

   APAC-ANZ:

   English, Dutch, German, French, Indonesian, Malaysian, Filipino, Vietnamese, Simplified Chinese

   C-ASIA:

   English, Arabic, Farsi (Iran), Russian, Turkish, Ukrainian

   RUSSIA:

   English, Russian

   CENTRAL-EUROPE:

   English, Croatian, German, Czech, Hungarian, Polish, Serbian, Slovak, Slovenian

   FRANCE:

   English, French

   ISRAEL:

   English, Russian, Hebrew

   S-E-EUROPE:

   English, Albanian, Bulgarian, Croatian, Greek, Hungarian, Macedonian, Romanian, Russian, Serbian

   S-ASIA-LEVAN:

   English, Farsi (Iran), French, Filipino, Hebrew, Hindi, Russian

   S-CENTR-AFR:

   English, Dutch, Farsi (Iran), German, Sesotho (South Africa), Zulu (African), Portuguese

   TAIWAN:

   English, Chinese for Taiwan
   
   
5. After you've selected that click Generate XML File.
6. Close A2 CDA Generator.
7. customize_upgrade.xml file will appear next to the CDA Generator:
   

Phase 2

For phase 2 you need "A2uploader" created by the_laser. If your antivirus pops up warning you that A2uploader is a virus, no worries, it's a false alarm.

1. Download the A2uploader, it's in a ZIP file so extract it
2. Launch the a2uploader.exe
3. Click "FileSystem Tool" on the right
4. Turn your phone off, remove and reinsert battery (do not turn it on)
5. Hold "c" key and while holding it connect your phone to the computer.
   (You might need SEMC Flash Device drivers if you haven't used Sony Ericsson Update Service before)
6. When you see activity in A2uploader screen (log lists on the left) release the "c" key
7. Navigate by double clicking: tpa/preset/custom
8. Drag and drop the customize_upgrade.xml file to A2uploader
9. Click Shutdown FS Manager (written in red)
10. Unplug your phone and turn it on.

Phase 3

To do the phase 3 you will need to download and install Sony Ericsson Update Service if you haven't done it before. Launch the program and follow the instructions it gives you.
It might report that your phone already has the latest firmware. That doesn't matter, just make it flash the phone anyway. After that all you need is patience and your phone is unbranded/debranded!