it does work dude!! after installing flasher pres winkey+r(run window) type cmd and press enter.. make sure u had "COPIED THE FLASHER FOLDER IN C:\"

in cmd windows type
cd Flasher
cd flasher-3.5.exe
then rename your image to a(vanilla) and b as(custom)
flasher-3.5.exe -F a.bin -f
it will say"suitable device not found,waiting..."

use that libusb thing and install "PC SUITE MODE(N900)"

u ll c it flashing.. since i have not included -R N900 wont restart.. after flashing remove battery and reinsert it again.. make sure your phone is still in off state(sometimes it might turn on :P)

then type
flasher-3.5.exe -F b.bin -f -R

use libusb and install "N900 UPDATE MODE"

thats it!!

if it doesn't work well i cant help.. sorry.. i miss my buddy(N900).. so i cant try it out.. good luck

PS: i accept your point that the command shell doesn't open.. there is one cmd file missing which win8 removes by default
PPS: try out all these steps in driver disabled mode!!!

i have updated my post do check it