I found this help guide
Here’s a tutorial that will teach you how to update your phone’s
firmware to a Nokia original version
(without your operator’s personalization) with NSU
(Nokia Software Update – the official Nokia program).
NSU reads the product code of your phone and it searches its database
for a newer version of the corresponding firmware in order to upgrade it.
This is why you will need to change the product code of your phone into a
non-branded product code, before running NSU.
Download the « NSS » software in order to change the phone’s product code.
This is a shareware program that you can download on the site of its author here :
After that, download the following program: gsm-magic (you might have to google it to get this download)
(this is not a crack, but a program that allows the activation of any disabled
option on no matter what program).
And finally, download NSU here: NSU.
NOW WE CAN BEGIN:
Connect your phone and wait for Windows to install the drivers.
Open NSS and click on “Scan for new device” on the right-upper part of the window
Click on the icon « Phone info »
Click on “Scan”
Open « gsm-magic » without closing NSS, then push the button « Enable » of “gsm-magic”.
As you can see, now you can change the product code (on the right of the « phone info »
window of NSS). For a Nokia 6680, type the product code 0521637
(this is the product code for France!) and then mark the case “Enable”.
Now press “Write”, and your phone’s product code will be changed
(you might think that nothing happened, because the phone is still in normal mode,
and the changing of the product code only takes a couple of seconds, but don’t worry,
the product code changed !).
Close NSS and “gsm-magic” and you can proceed now with the NSU flashing.
When the flashing with NSU is over, start-up your phone and you’ll have the pleasant
surprise that your phone’s firmware is the latest Nokia non-branded firmware in date!
NOTE: I advise you to disable any antivirus and firewall on your PC during the flashing.
In order to find out the product code for other phone models,
download the firmware for your phone model, connect your phone to NSS, click « Scan »,
then « Flash », and after that look for your product code when on « Market »
you will see your country. Write down this number, then you can start the manipulation as
described above. Anyway, we will soon have the product codes for all the models,
so we won’t need this step.
Product code E61 0529663
product code N70 0523982
product code N80 0526966
product code 6680 0521637
product code 6630 0518104