I originally followed the instructions included with the EFI bios file that is found on ASUS website under "Services"; "Support"; "Download"; and then of course you are given the choice of selecting your product e.g. motherboard, series, and then your specific P5Q board and OS you are using, etc,
I ran into a little snag however with mine, maybe it was me, maybe my board, or Maybe it was a step omitted that requires your USB drive be bootable (utilizing like FreeDos) to change from Legasy bios to EFI-Bios, as others use their USB drives to upgrade their legasy bios files all the time using I guess the Afudos utility. (notice the DOS) LOL
I was finally able to change from the Legasy bios to the EFI-Bios once I followed this http://ubuntuforums.org/showthread.php?t=484774
to make my USB drive bootable, and then downloading and unzipping the required files to the USB flash drive.
For whatever reason I thought the EFI-bios would be more, (so much for not researching it first
); it is however a GUI style bios, allowing one to use their mouse and or keyboard to navigate and tweak the bios, that is provide your mouse works, which my USB wireless mouse didn't until I changed the setting in the bios for USB devices navigating with my keyboard.
I also had to tweak/select which RAID setup it used as I am messing with ASUS Drive Xpert and Intel Matrix Storage, it defaulted to the Drive Xpert and I have been using Intel Raid for my main one right now.