IT all depends on what you are flashing.....IMO Yes you should do it in dos, but I have flashed lots of times in windows..... If you want say more voltage. Then you need to do that in dos with -newbios That will force the card to take more voltage. Say you just wanted to change the speed of the fan or clocks you can do that in windows. What he is really telling you is that more can go wrong flashing in windows than in dos. There are more languages the machine has to talk down to before it can even flash your video card in windows, than there would be in dos mode.