Okay basically here are instructions for YOU using Windows xoi99 if you wish to follow them.

1) Go here: http://tablets-dev.nokia.com/maemo-d...-downloads.php and download and run maemo_flasher-3.5_2.5.2.2.exe to install Maemo Flasher 3.5 to Windows.

2) Go here: http://tablets-dev.nokia.com/nokia_N900.php and enter your phone's IMEI number for verification purposes. This can be found either inside your phone underneath the battery or by going on to phone and entering *#06#

3) Download the latest version of firmware; where the "Brief Description" is PR 1.2 version 10.2010.19-1 of your desired region, such as UK or US. Save the .bin file to the Maemo Flasher directory for ease of use in the next steps.

4) Now, ensure your N900 is powered off. Hold down "u" on the N900's keyboard, connect the USB cable to your computer and N900, whilst continuing to hold "u" down. It will now be ready for flashing, the backlight will tend to be off but the screen is still on when this mode is entered. You should be able to see the USB icon in the corner of the screen on the N900.

5) Now, the fun part: run Maemo Flasher 3.5 from the Start Menu on your computer and in the command prompt which pops up, type:

flasher-3.5.exe -F <name of .bin file here> -f -R

So if you wish to flash the UK version of the firmware, after you have downloaded the appropriate .bin file you would type:
flasher-3.5.exe -F RX-51_2009SE_10.2010.19-1.203.1_PR_COMBINED_203_ARM.bin -f -R

The flasher will then keep you updated, taking no longer than a few minutes.