craigh,
What are you referring to? Section 2-5 of your manual page 50? where it shows your Boot Options and boot devices with UEFI/Legacy designations preceding a device. Drill down and look closely at each device and option. Or, do you have a specific BIOS setting that allows you to specify if the BIOS with operate in UEFI or Legacy mode? I downloaded your MB manual, but didn't see a specific settings. Maybe this has been implemented in a later version of your BIOS? My BIOS has this option... Asus...... Yours may not, I am just trying to get clarification on the exact setting you are referring to.
You will want to set the BIOS for Legacy Mode operation (if applicable) and install to a Legacy device (your SSD). This will install the 100mb System Reserved and OS partition I described previously.
Since the BIOS itself is UEFI capable, devices that support UEFI will be designated this way and will allow for and take advantage of these features. Depending on implementation, each device should (not will) have two designations in BIOS. One for UEFI and one for Legacy... if supported.
You'll want Legacy if installing Win7, to a MBR, NTFS formatted disk.