Guys I just found an alternative solution that doesn't require much preparation. I haven't checked if it is already mentioned in the thread. This is how i fixed my 5850 without needing to go to DOS mode.
First you must have access to your desktop of course (Remove the card and change the primary adapter to i-gpu in the bios. Save, turn off the power, put the graphics card, restart again) (Also switch the cables from your graphics card to the i-gpu)
Then download atiflash and extract it. Don't forget to download the bios too!
Next create a shortcut of ''atiwinflash.exe'' in the same folder.
Next step is to right click the shortcut, click on properties, and in the destination box, add this in the end: atiwinflash -f -p 0 bios.rom
*Note that bios.rom is just a random name. In order to work. The bios must be in the atiflash folder and to match the shortcut's bios name.
Now run the shortcut as administrator (right click->run as adminitstrator), and the flash will begin.
If everything is done correctly the program should display a message with the new values.
Restart and change the primary adapter back to pci-e. And don't forget to switch the video cables from your i-gpu to your graphics card.
You should have access to your desktop now.