If you mean you can't use 700 GB
If your system supports UEFI , it should be enabled in the BIOS.
But dont change it now, otherwise windows wont boot
And if the hdd isnt formatted in GPT, you wont be able to use all of it
2.2 TB is the limit for mbr formatted hdd's.
If you want the rest (if this is your bootdisk), you'll have to do a clean install change to UEFI in the BIOS first before you install windows. If Win8 x64 is on this