Step 1: download firmware
fw v4.4.0:
– File system.img.gz (Google Drive)
– File boot.img (Google Drive)
– File fastboot.img (Google Drive)
Step 2: download adb + fastboot
http://download746.mediafire.com/z17f7s59n30g/x5h0ba1aw0ddc5b/adb.rar
Step 3:
Unrar file adb.rar then place 3 files system.img.gz, boot.img, fastboot.img in same folder with adb + fastboot
Step 4:
Hold Shift and right click on empty zone, then click Open command window here
Step 5:
Enter DROIDBOOT (power off, hold power and volume +)
Plug with your PC
Step 6:
Use these command lines:
fastboot erase cache
fastboot erase userdata
fastboot erase system
fastboot flash boot boot.img
fastboot flash fastboot fastboot.img
fastboot flash system system.img.gz
fastboot flash boot boot.img
fastboot flash fastboot fastboot.img
fastboot reboot
Done!