There are so many variants it would be best to know the die's R designation. If its an R430 based die and you flashed an R480 its probably going to be a goner because those are two different chips on two different processes.
I'm sorry I tried looking the models up but it can be time consuming.
But i believe I had a card that yours was based on. The x800xl and it was the 110 Nanometer PCI-E version of the R420
Here has been my experience with bios flashing.
Never use a floppy they die all the time. Setup a pen drive for floppy duties.
Never use winflash to many issues.
You shouldn't have needed the reboot command.