Here's a tutorial that explains you how to flash K750 to W800.
WARNING!!!
YOU WILL PROBABLY LOSE YOUR PHONE'S WARRANTY.
FLASHING SE K750 to W800 (CID 49 EMEA 2) by ama95
ALL FILES FOR DOWNLOAD ARE IN TOPSONY DOWNLOAD SECTION
How to get access to Download Area? - Top Sony Forums
Glossary
w800 - phone model
r1bc002 – firmware version
fs/main – type of file
emea2 - region
cid36/49 – protection type
EMEA1 - en, pl, lv, lt, ru, et, uk
EMEA2 - en, cs, hr, sr, sl, sk
EMEA4 - en, bg, hu, ro, ru
EMEA6 - en, ar, fa, fr, ru
• Connect – connecting phone to pc over usb by holding c button
• Disconnect – disconnecting phone from usb cable
• Reset – reinstert the battery
1. Getting ready
Download:
XS++ 3.1 (Darwin)
w800_r1bc002_main_eu_emea cid49
w800_r1bc002_fs_emea2 cid49
Extract and run XS++
Plug your USB cable only in PC
Turn off you phone and take out the SIM and Memory Stick.
Make reset.
Your phone is turned off during the flashing.
Backup all contacts, messages etc. Flashing will delete them and all files in phone’s memory.
2. Flashing Filesystem
Click Start. You have 30 seconds to connect. Mark Flash File System. Open File System file (w800_r1bc002_fs_emea2 cid49). Click Flash. Follow the instructions and when program says Finsing flash click Stop. Ignore the error. Make disconnect then reset.
3. Customizing File System
Click Start. Connect. Now mark Customize File System. Choose Phone Model (W800) and CDA and Region (EMEA_2). Click Flash. Follow the instructions and Disconnect your phone when program says so. Make a reset.
4. Flashing MAIN
Click Start. Connect. Mark Flash Main. Open MAIN file
(w800_r1bc002_main_eu_emea cid49). Click Flash. When program says Finishing Flash disconnect your phone. You’re finished! Insert SIM and Memory Stick and turn on your phone.