Missing RAM in Windows 7

[MojoPin]

Hello
I've recently built a new PC, installing 8gb (2x4) Corsair RAM (http://bit.ly/g1pj3L) into a Gigabyte P55-UD5 motherboard.
The BIOS says there is 8gb, and in Device Manager 8gb is detected, but it says "(3.99gb usable)" next to the total.

I've installed and reinstalled Windows 7 64-bit three times now, updated BIOS, and drivers too. Common solution is to untick a box in MsConfig too, but this is unchecked on my system.

What can I do to get all 8gb working? Any ideas please?

Thanks in advance.
Andy

 

[MojoPin]

Thanks for your replies.
@muksh11
@EGuitarStar - Definitely is the 64bit version
@hyperst I have slightly over-clocked, but the problem was there even when the processor was out of the box.
@hawker1986 I have a terrible feeling you're right!

The thing that puzzles me most is that Windows and the BIOS detect how much RAM there is, 8gb, but that only 3.99gb is usable. Surely if it was faulty or connected improperly, the system wouldn't be able to detect both sticks?

 

[MojoPin]

There are several options, the main one being to install an XMP profile. Without this enabled, the memory runs at a much lower speed. Enabled, and it runs at 2000Mhz.

What is memory remap? (thanks, by the way)