ATiFlash Help! Borked 5850

Hello, I'm hoping someone can really help me out. I recently flashed my 5850 toxic -yes in windows- and was successful but tried to re flash it so I could adjust the voltage and when I went to reboot I get a black screen. my bios post stops when it gets to vga bios and i know I stuffed up somewhere.
I do have another pci-e card (x1950xtx) which I 'm using atm.
if I also add the 5850 in the second pci slot with all power cords attached and start the comp it will again stop at trying to read vga bios. If I remove one power cord from the 5850 (6pin) I can get it into windows.
GPu-z wont recognize that I have 2 cards on mobo even if I reattach the power cord to 5850 while in windows.
I have made a bootable usb with a bios for the toxic 5850 from sapphire and on my first attempt stuffed up another x1950xtx(I had 4 now 3 surviving) as i just "flashed" and i think it tried to flash the X1950 instead of the 5050.

Can anyone guide me PLEASE?

Is there a way to flash the second pci-e slot while using the first slot so i can see the screen in DOS?
or does DOS have to recognize that theres another gpu on the motherboard and how is that acheived?

Man I've already think I've created 2 bricks and dont feel like building a house, so any advice would be mostly appreciated.

Thanks for the reply erocker.

I'm trying to re-set the bios on the 5850 at the moment, my problems started when I tried to re-flash the 5850 as I noticed I couldnt adjust the voltage in msi afterburner.

I tried once already to flash in DOS with another X1950xtx in slot #0 and my 5850 in slot #1 but I think it tried to flash the 1950 and I couldnt reboot. took out the 5850 and left the 1950 inside and it went to black screen with the bios post stuck on vga bios-so I think I stuffed that first X1950 aswell

I now have my other X1950xtx in slot #0 and want to make sure I dont stuff another one.
Do I attach the 6pin power cords to both cards when I try your recommendation or only have power on the X1950xtx?

When I do have all cards powered up my system wont boot into where I can get into the setup. The post bios checks cpu, Dram and then stalls on VGA bios.
Is there a way of getting to DOS without having my bios boot from usb as priority?

I'm not sure if that will work as it still does its preliminary checks before anything comes to screen and when I get the logo on screen i can then go into mobo bios or let it carry on with the boot.
If I disconnect one 6pin from the 5850, let it boot from usb then re-attach the 6pin to the 5850 do you think it will work?

Also does it have to be AtiFlash as i'm using the Hbusbfw that I downloaded from Sapphire, would the same commands work?

Thanks again.

I used atiflash and loaded all relevant files to a bootable usb.
When i'm in DOS it reports "no adapter found" and error of "oflo1"
I also used commands -i and -t and had the same message of no adapter.

Can anyone help please?

Thankyou Erocker, My mobo has 2 pci-e slots. i just tried flashing to #2 but still get the "no adapter found" and error OFLO1.
just also read in another thread someone with similar problem and tried his method of using all the F commands -fa -fm -fp -fs in one command but still no luck.
Ive been unable to retrieve the original bios and downloaded one from sapphire, its a .T4A file and not a .bin or .rom file would this be a problem also?

I have my fingers crossed.

my mobo:http://www.techbuy.com.au/showproddetails.asp?prodId=78011

Excellent it worked!!
Finally got the damn thing to flash, not sure how exactly it happened but I went into Bios and changed this setting called Addon ROM Display Mode from Keep Current to Force Bios.
when I restarted I noticed both cards fan were at normal speed and I didnt have to unplug a 6pin cord from the 5850. Furthermore it booted into DOS without a hicup.
I used the command C:/atiflash -p -f 1 toxic.t4a
and had a successful result. So it looks like you can use the t4a file after all which was good 'cos I couldnt change it anyways.

Just wanna say thankyou for helping me and I hope this may help someone else who may get into the deep end like me.