8GB of RAM installed (4GB usable)

Hello, after uninstalling and reinstalling Windows, I'm still having the same problem

in system information it says 8GB of RAM installed (4GB usable) :( yet I

am running Windows 7 Home Premium 64 bits. So I would like to know if you could

help me find a miracle solution and/or give me the frequencies or the voltages

(the numbers) to enter in the BIOS in the RAM options, etc. Thank you very much.

here is my config:

Windows 7 Home Premium Edition (x64) (build 7601) Service Pack 1
Default web browser: Google Chrome
Default email client:
WinSAT
Overall score 5.5 (Processor: 7.4, RAM: 5.5, Graphics: 7.8, Gaming graphics: 7.8, Main hard drive: 5.9)
Motherboard
SMBios version 2.6
ASUSTeK Computer INC. P7P55D Rev 1.xx
Bios: American Megatrends Inc. 2003 12/14/2010 size: 2048Kb
Chipset
Northbridge: Intel DMI Host Bridge
Southbridge: Intel P55
Processor
Intel Core i7 860 Lynnfield Socket 1156 LGA (@45 nm) 2800 Mhz (L1I: 4 x 32 Ko, L1D: 4 x 32 Ko, L2: 4 x 256 Ko, L3: 8192 Ko)
Memory
Total physical memory: 8192 Mo, Type: DDR3, @663.8MHz, 9.0-9-9-24-2T
DDR3 Corsair CMD8GX3M4A1333C7 2048 Mo PC3-10700H (667 Mhz)
DDR3 Corsair CMD8GX3M4A1333C7 2048 Mo PC3-10700H (667 Mhz)
DDR3 Corsair CMD8GX3M4A1333C7 2048 Mo PC3-10700H (667 Mhz)
DDR3 Corsair CMD8GX3M4A1333C7 2048 Mo PC3-10700H (667 Mhz)
Graphics Card
Radeon HD 5870 (RV870, 1024 Mo)
ATA Devices
SAMSUNG HD103SJ 1AJ100E4 (SATA II, 931.51 Go, Cache: 31 Mo)
CD/DVD Drives
TSSTcorpCDDVDW SH-S223C SB01 (DVD+R/DL Recorder)
Hard Disk
SAMSUNG HD103SJ ATA Device
PCI/AGP Cards
Storage
Intel Corporation: 5 Series/3400 Series Chipset 4 port SATA IDE Controller:
Intel Corporation: 5 Series/3400 Series Chipset 2 port SATA IDE Controller:
JMicron Technology Corp.: JMB362/JMB363 Serial ATA Controller:

Network
Realtek Semiconductor Co., Ltd.: RTL8111/8168B PCI Express Gigabit Ethernet controller: M4A785TD Motherboard

Display
ATI Technologies Inc.: Radeon HD 5870 (Cypress):

Multimedia
Intel Corporation: 5 Series/3400 Series Chipset High Definition Audio:
ATI Technologies Inc.: Cypress HDMI Audio [Radeon HD 5800 Series]:

Bridges
Intel Corporation: Core Processor DMI:
Intel Corporation: Core Processor PCI Express Root Port 1
Intel Corporation: 5 Series/3400 Series Chipset PCI Express Root Port 1
Intel Corporation: 5 Series/3400 Series Chipset PCI Express Root Port 5
Intel Corporation: 5 Series/3400 Series Chipset PCI Express Root Port 6
Intel Corporation: 5 Series/3400 Series Chipset PCI Express Root Port 7
Intel Corporation: 5 Series/3400 Series Chipset PCI Express Root Port 8
Intel Corporation: 82801 PCI Bridge
Intel Corporation: 5 Series Chipset LPC Interface Controller:
Intel Corporation: Core Processor QuickPath Architecture Generic Non-Core Registers:
Intel Corporation: Core Processor QuickPath Architecture System Address Decoder:
Intel Corporation: Core Processor QPI Link 0:
Intel Corporation: Core Processor QPI Physical 0:
Intel Corporation: Core Processor Integrated Memory Controller:
Intel Corporation: Core Processor Integrated Memory Controller Target Address Decoder:
Intel Corporation: Core Processor Integrated Memory Controller Test Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 0 Control Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 0 Address Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 0 Rank Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 0 Thermal Control Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 1 Control Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 1 Address Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 1 Rank Registers:
Intel Corporation: Core Processor Integrated Memory Controller Channel 1 Thermal Control Registers:

System
Intel Corporation: Core Processor System Management Registers:
Intel Corporation: Core Processor Semaphore and Scratchpad Registers:
Intel Corporation: Core Processor System Control and Status Registers:
Intel Corporation: Core Processor Miscellaneous Registers
Intel Corporation: Core Processor QPI Link
Intel Corporation: Core Processor QPI Routing and Protocol Registers

Bus Series
Intel Corporation: 5 Series/3400 Series Chipset USB2 Enhanced Host Controller:
Intel Corporation: 5 Series/3400 Series Chipset USB2 Enhanced Host Controller:
Intel Corporation: 5 Series/3400 Series Chipset SMBus Controller:
VIA Technologies, Inc.: VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller: M4A series motherboard
USB Device
Microsoft Corp. Xbox 360 Wireless Adapter (Xbox 360 Wireless Receiver for Windows)
Logitech, Inc. Logicool HID-Compliant Keyboard (106 keys Ctrl+Caps) (USB composite device)
Logitech, Inc. Logicool HID-Compliant Keyboard (106 keys Ctrl+Caps) (USB input device)
Logitech, Inc. Logicool HID-Compliant Keyboard (106 keys Ctrl+Caps) (USB input device)
USB composite device
USB input device
USB input device
USB input device
Intel Corp. Integrated Rate Matching Hub (Generic USB Hub)
Intel Corp. Integrated Rate Matching Hub (Generic USB Hub)
Keyboard
PIH keyboard device
PIH keyboard device
Mouse
HID mouse
HID mouse
Screen(s)
Generic Plug-and-Play Monitor (Samsung SAMSUNG)

Configuration: Windows 7 / Safari 535.1