This is a video tutorial on how to flash Nokia N900 completely. Here I'm flashing using the Global firmware. If you don't have Skype pre-installed, its a good idea to flash it using a global version since it includes Skype.

Things needed

  1. RX-51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM.bin

  2. RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.bin

Both of these can be obtained from tablets-dev.nokia.com.
  1. flasher-3.5 which can be obtained from maemo-dev-env-downloads.
For detailed reference you can go to maemo wiki.

Flashing procedure

  1. Install maemo flasher.

  2. Switch off the device, press u on the phone's keyboard and plugin via USB. The phone will boot with a USB icon on the top right corner.

  3. Run the following commands as required.

NB: The commands for flashing are (in order): 
flasher-3.5.exe -F "path to eMMC image (vanilla)" -f
which is for flashing eMMC, and then 
flasher-3.5.exe -F "path to Combined image (fiasco)" -f -R
for flashing the OS. To flash the OS only, run the second command (fiasco).
It is not recommended to only flash the eMMC (user content). So in that case, we need to flash the OS as well.

Video tutorial.

If not able to view the video, install Flash Player Projector Content Debugger from Adobe and run the swf.

Update on Fri, 10 May 24: Flash player is no longer supported by Adobe. However the last working version can be installed and it continues to work. But I am not sure if it runs on ARM macs.