I ran apt-get update then apt-get install nitdroid-installer and it went fine. the installer stops while formatting ext3, so I tried (Step 1 Partition 1-3 and reboot) here:http://wiki.nitdroid.com/index.php?title=N900-install
but I am stuck again.
When I do umount /dev/mmcblk1p1, it says umount: cannot umount /dev/mmcblk1p1: invalid argument, I think this is because my memory card is not currently being detected by the device, I have had this problem before, will let you know what happens