Windows 7 x64 only recognizes 6 out of 8 gb ram

Here are my specs:

ASUS P6T X58 ATX LGA1366 DDR3 3PCI-E16 PCI-E1 2PCI CrossFire SLI SATA2 GBLAN Motherboard
Intel i7 930
ATI Radeon HD5770 850MHz 1GB GDDR5 4.8GHz
Western Digital Caviar Blue SE16 640GB SATA2 7200RPM 16MB
Corsair TX750W 750W
Corsair CMP8GX3M4A1600C8 Dominator 8GB 4X2GB DDR3-1600 CL8-8-8-24 Core i5 i7 Dual Channel Memory Kit

I bought this computer recently and after a fresh install of Windows 7 x64, I found that Windows only displayed 6gb of ram. BIOS reports 8gb of ram and I'm not sure if I did any tweaks, but after a restart Windows displayed 8gb so I have left it alone since then. I decided to check again today and it reports 6gb again. BIOS still reports 8gb of ram though.

Also, only 4gb is usable in msinfo32? I am running 64-bit and I don't have faulty ram.

I have close to that setup, same ram, same or similar MB but an i7 and 12 gig of ram (in triple channel mode).

I didn't do anything fancy in Windows itself, and the only thing I did in the BIOS was turn on AHCI.

Windows reports 12 gig of ram, 11.8 usable.

Believe it or not I turned on AHCI after install and had no troubles but I would look up oin the tutorials section here about how to safely turn it on after install if you want to try that...

I'll give it a try, do you have a link to the tutorial or direct me in which section I could find it?

This is the tutorial:

AHCI : Enable in Windows 7 / Vista

However it really is just a feature for improving harddrive performance over IDE.

So it really /shouldn;t/ have anything to do with how much memory your seeing, it was just the only posible difference other than the i5/i7 between our machines.

It is always possible that you do have a bad ram stick, unless you;ve actually done like 12 hours of memtest32 on it.

Also, it's always possible that a piece of lint got into a ram socket before you snapped the ram in or something like that.

I decided to reseat my RAM and 8gb appears again. The RAM may have been jostled a bit since I have moved it from my house to my parents house and back recently. Thanks for the help