Downloaded through, decrypted and repackaged by Flashtool.
Android version: 4.4.4
Kernel: 3.4.0-perf-g1bb39c2 [email protected]#1 Mon Sep 22 12:25:55 2014
Build number: 10.5.1.A.0.292
Customization Version: 1270-7280
Branding: Generic NCB
Country: Nordic Combined
This works on ANY Xperia Z (C6603).
Your Xperia Z does NOT have to be rooted.
Your Xperia Z does NOT have to be bootloader unlocked.
This does NOT re-lock a SIM unlocked phone (unlocking is ONCE and PERMANENT).
This does NOT unlock your bootloader.
MD5 of FTF file: c5c8e091192718e7d2afdab36feef29f
I advise checking the MD5 sum of the file you downloaded matches the above value with md5summer or similar software of your preference before you flash it.
How to flash stock roms with Flashtool
How to root 10.5.1.A.0.292
If you are flashing this over a newer firmware version, then a full wipe is essential.