Hi Sean, did you reach any conclusion over prefetch / superfetch? I notice that SSD Tweaker's auto tweak settings recommend disabling prefetch completely and setting superfetch to application only.
For CD/DVD-ROM drives, if you insert a Windows 7 x64 installation disc to it, you will see an icon of the drive in the Boot Priority section of UEFI with the "UEFI tag". You will also see an icon of the drive WITHOUT that tag. So if you want to install an OS to a GPT partition you need to boot WITH the icon that has the UEFI tag. Also, only Windows 7 x64 supports booting with GPT. Obviously, your motherboard should be capable of using UEFI (instead of BIOS) in order to boot with this kind of partition style.
If the CD/DVD-ROM drive doesn't have any disc inside, you WILL NOT see the icon with the UEFI tag in the Boot Priority section.
For Windows x64 installations copied to USB drives using the official Microsoft tool, you need to format your USB drive with FAT32. Formatting it with NTFS, copying over the files, and booting with it WILL NOT display the CD/DVD-ROM drive with the UEFI icon. You do not need to use the "Launch EFI Shell from filesystem device" to do a UEFI boot.
I hope this clears a lot of confusion with this. You can also read a lot about it here:
For downgrading the BIOS, you should follow this guide: http://hardforum.com/showthread.php?t=1629404 . It is for the P8P67 motherboard but it worked flawlessly on my P8Z68-V motherboard.