Win7 (pro 64bit) recognizing all 12GB but saying only 6GB is usable?!

Hello

I recently just finished building my machine

Gigabyte GA-X58A-UD3R motherboard
12 GB (6x2GB) G.Skill ddr3 tripple channel memory

Got windows 7 professional 64 bit installed

Went into system specs and it says "12GB (6GB Usable)

I updated the bios to F5 and rebooted, it showed all 12GB usable!!

I shut down the machine, woke up this morning turned it on, and back to 12GB (6GB Usable)

I went into msconfig, boot, and made sure the max memory is unchecked.

Ive searched and seen this problem, but Ive yet to find any solutions.





Please help