Something else I should mention. For those of you who are looking for an alternative to the .EXE file that you download online, which supposedly flashes your stock HD 7970 with the GHz BIOS:
Follow the steps in the OP. Instead of the stock BIOS of your card, chose
this one instead. Flash this as your second position on your dual-bios switch and BAM, you now have an ATi Radeon HD 7970 GHz Edition card. Windows should try and install new drivers once you boot into Windows with the new BIOS flashed.
This process SHOULD work on every HD 7970. You may, although, need to reinstall Catalyst drivers if you plan on flashing the BIOS to one other than the one designed for your card.