This is my own take on the subject and as always in these matters you undertake any action at your own risk!
I assume that you have a broadband connection!
(Windows Vista users please note.
There are some reported issues with NSS and Vista, namely the installation of the NSS driver, and I am investigating this. I will update this guide when I have hard evidence of any problem. In the meantime would Vista users please give me feedback on this subject)
ZXON reports that he uses Vista Business and NSS v188.8.131.52 with great success.
Many thanks for the feedback!!
Well, it gets rid of those anoying network boltons and quirks that they insist on giving us, just so we remember who we got the phone from! Duhhh! It also allows you to ugrade by the generic firmware path!
This is 'slightly' more serious stuff. With an upgrade you get the latest firmware tweaks before (sometimes well before) the networks release their branded version. This means you can take advantage of improvements as soon as they become available!
Are there any drawbacks to this procedure?
Mmmmm! There has been concern about loosing warranty rights by doing a debrand or upgrade. I believe you still have the same rights as before as you haven't done anything you wouldn't do by going through the network release upgrade process except for debranding!
So you may loose the warranty through your network provider, but, you would still have your Nokia warranty to fall back on! You decide if the benefits outweigh the risks!
So having got that out of the way -
How do you do it?
You need to be connected to your PC and have Nokia PC Suite running and your phone recognised.
Switch off any Anti Virus and disable any firewall!!!!!
Firstly you will need to Sync your stuff with PC Suite.
DO NOT use backup and restore as this has shown to cause future problems with stability!
If you need your texts message for reference then change the message settings to save on your memory card and you get the option to copy across all existing texts.
You will also 'loose' all your installed apps and will have to reinstall these once you have completed the Debrand/upgrade process.
You will also need all your network and internet (data) access settings. You can note them down, get them resent after the debrand/upgrade to your phone by text message from your network provider or from Nokia, or simply get them from here http://www.filesaveas.com/networks.html.
Next step is to download a programme called Nemesis Service Suite (NSS) from here http://www.b-phreaks.co.uk/files/NSS/NSS103812.zip
Unzip this to a folder that you can find again! Install the application. You may be asked to install the NSS drivers for the N95 so do this when prompted.
Now run NSS and you are starting the debrand process!
When the main NSS window comes up in the top right click scan for new device. Your phone should be detected.
Next click the 'Phone Info' button. This will give a pane to the right of the window and ready should be flashing on the bottom bar. Click the 'Read' button under 'Production Data Edit'. this brings up some phone info including the important 'Product Code'. Your code will relate to your country and network provider and it is this we need to change!
This forum page http://www.allaboutsymbian.com/forum/showthread.php?t=58225 will give you a list of product codes. (while you are on that page consider joining the forum for future assistance).
For most people the generic EURO1 code is what we want so note it down (it doesn't matter whether you use the sand or plum code)!
You now need to input the code in place of the one that NSS returned against it's 'Product Code'
box! Copy and paste will do it! Tick the enable box alongside and then click the 'Write' button. When finished 'Write new values........Done' will appear in the bottom bar at the left. Your 'new' product code will now be shown in the 'Product Code' box.
Your phone is now ready to be upgraded to the latest official Nokia generic firmware release.
Close NSS and open Nokia PC Suite!
Make sure your battery is fully charged.
Click the 'Update phone software' button and the programme will lead you through the process of update. You may be required to download and install a newer version of the 'Nokia Software Updater' so just agree and wait for this to complete.
The NSU (Nokia Sofware Updater) will start and give instructions! It will detect your phone, identify it and search for an available update. Then, if one is available, it will give the option of proceeding with the update. Say yes and once the update has started wait until the process has finished.
Do not touch the phone, do not turn it off, do not disconnect the USB cable.
When the update has finished your phone will restart and you will have installed the latest firmware version of the Operating System.
At this point it does no harm to do a hard reset (see below) just to be sure you have what is refered to as a 'vanilla' phone.
Now re-sync with PC Suite and re-enter your network access and data settings.
Finally, re-install your applicationsto the phone memory (if you use the card memory you can get problems and power consumption goes up so less battery life!
And that's it! You should end up with a stable and zippy phone and the minimum of problems!
I hope all this helps and to anyone undertaking the procedure "GOOD LUCK"
Here are some useful 'Codes' that will interogate the phone -
*#06# gives your IMEI (serial) number.
*#0000# gives firmware and phone version.
*#2820# (*#BTA0#) To view Bluetooth device address.
*#62209526# (*#MAC0WLAN) To view the MAC address of the WLAN adapter. This is maybe necessary for wlan encrypted setup.
*#92702689# (*#WAR0ANTY#) To view the life timer information. This is the total time of phone calls in minutes.
Warning : All old data will be lost when hard reset is used.
*#7780# : Soft Reset. Restores ini files from rom but preserves user data (photos, 3rd party apps etc).The phone will ask you a confirmation, enter a security code which is 12345 by default.
*#7370# : Hard (sometimes called 'Deep') Reset. You will get a format of the C: drive. Everything on the drive will be wiped and clean default files will be rewritten. You will be asked to input a security code which is 12345 by default.
There is another method of hard resetting the phone (similar to #*7370#). It is useful in some cases, for example when the phone cannot reboot. Switch off the phone then press and hold Call key (Green key) + * key + 3 key + power button for a couple of seconds. If you hold these buttons until 'Formatting' is shown you will get the same result as using *#7370#