Flashing a WP8 Nokia Lumia phone
is explained in this tutorial. Thanks to Nokia Care Suite (NCS) you can flash your phone yourself at home with any valid firmware you like, be it stock or custom (modified). This is also helpful for flashing a firmware meant for a different RM on your phone, thus de-brand it and add additional RM-specific features to it.
Obtaining Firmware Files:Get Navifirm+ from Attached below
Open it, select Nokia Care Suite from the drop down menu in top-left.
You well see a list of phones on the left. Select your phone.
You well then see the available software for it on Nokia server. Select the one you want to install. (REMEMBER : Downgrading may kill your phone, so always flash either the same firmware version your phone is on, or newer)
You’ll see the available variants of the update. Select any! and download all the files.
Place the files in the directory : C:\Documents and Settings\All Users\Application Data\Nokia\Packages\Products\[Your Phone RM]
Flashing Firmware Files:
Download Nokia Care Suite 5.0
Open it, click on File->Open Product, select your phone.
Right click on the Programming button on the left. Click on Recovery.
Click Update List, and select the firmware it finds.
Check update automatically and USB dead phone flashing and click next.
Follow the on-screen instructions and turn your phone off.
It will say application has lost the connection with your phone. Turn your phone on at this point holding the volume-up button and quickly press retry.
You will see the flashing procedure starting and it will be finished within a few minutes and your phone will be ready to use.
NOTE: DO NOT FORMAT