Find out from the manufacturer how to boot from a USB drive. Then make a bootable flash drive on another computer like this:
1. Make a USB bootable drive using this creator:
USB Boot drive (HPUSBFW)
2. Then download the boot files and extract them to a folder of your choice
3. Run the HPUSBFW program.
Select the correct USB device from the drop-down menu, set file system to FAT32 and check Create a DOS startup disk.
4. Then browse for the extracted boot files (now in the folder of your choice) and press start to begin formating it.
5. Put Atiflash onto it along with the original bios (can be DLed here). Make sure to name it something easy like "bios".
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6. Then put the USB drive in and hit the key to make it bootable (for my motherboard it is F8).
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7. Wait a few minutes for the Dos to load and type: atiflash -p -f 0 bios.rom
8. Then wait about 5 minutes for the flashing to complete and reboot.