There is a small guide at the end of the first post here: [url=http://www.techpowerup.com/forums/threads/vbe7-vbios-editor-for-radeon-hd-7000-series-cards.189089/]http://www.techpowerup.com/forums/threads/vbe7-vbios-editor-for-radeon-hd-7000-series-cards.189089/[/url]
Additionally you can check another site with more insight into what to edit and what settings to use: [url=http://www.cryptobadger.com/2013/10/undervolting-in-linux-via-modified-bios/]http://www.cryptobadger.com/2013/10/undervolting-in-linux-via-modified-bios/[/url]
But you can use the second guide with all the software mentioned in the first one under Windows!
Hope that helps!