Quote Originally Posted by BeepBeep2 View Post
Read the help part and find out all of the adapters...it's a system information command. I forget what it is. If you don't see the ATI card listed (along with adapter number) you won't be able to flash it.
That was the -i switch, wasn't it? OP, just try the -i switch, and see which adapters it lists. If you have the correct adapter number for your 5850 in that list, you can force the flash with:

atiflash.exe -p <adapter number> -f <biosname>