By default you can’t install DEB files directly on the N900, to do this you need to switch to RED PILL mode (remember The Matrix film you had the choice to take the RED PILL or the BLUE PILL).
To enable RED PILL you need to goto Application Manager and create a NEW application catalogue and in the web address type ‘matrix’.
You then just click off the menu and you are given to choice to choose the RED or BLUE PILL.
Select the RED PILL and when you select the bar again at the top of the Application Manager you will see an option to Install From File 🙂
Once the application is installed remember to repeat the process above return to the BLUE PILL.