OK read this link first http://wiki.maemo.org/Updating_the_tablet_firmware then you want to get the correct firmware for your device

TAKE A BACKUP FIRST USING THE BUILT IN APP!!!!!

1) Go into settings->about product... make a note of the version: if your with vodafone it should end with something like 205.1

2) Download the latest UK vodafone firmware http://tablets-dev.nokia.com/nokia_N900.php Note: you will need your IMEA to get the file

3) you need a windows xp machine (can be a vmware image), make sure its SP3 as SP2 has issues.

4) Download and install the flasher tool from here http://wiki.maemo.org/Documentation/..._documentation

5) Move the firmware into the installation folder for the flasher app.

6) open command prompt and make sure the path is the flash app folder were you moved the firmware to.

7) power off your mobile

8) type: flasher-3.5.exe -F <enter firmware here> -f -R

9) connect phone with usb, hold down 'u' key

10) once phone reboots your done.

RESTORE BACKUP TO GET ALL YOUR APPS, SETTINGS, CONTACTS etc back.

If you are unsure of any of these steps DO NOT PROCEED! Ask first.