Systems Management

I have a Dell XPS computer (Windows 7 64 bit) that I just installed 24GB of RAM (replaced 6x2GB sticks with 6x4GB sticks). After installing the memory, I booted the computer expecting to see the "your amount of memory has changed..." but did not. After the computer booted, I checked the Windows properties. It read: "Installed memory (RAM): 24GB (7.99 GB usable)". I Googled the message and followed the instructions to update BIOS and verified the Maximum Memory (in msconfig) was unchecked. I looked through the BIOS settings for memory remapping but cannot find anything in the BIOS showing that. The BIOS show 8GB of memory. I called Dell for support only to be told that this is a known issue with Windows 7 and that I should disregard the discrepancy. That didn't sound right to me so I continued researching and have not found a single article stating this was a known issue.  Additionally, if it was a Windows issue, that should not affect what the BIOS are showing.  I then removed the new memory and reinstalled the old memory (6x2GB sticks).  The BIOS now show 12GB and Windows shows 12GB usable memory.  I purchased the memory from Dell and was told this is the correct memory.  I have posted my hardware info below:

Operating System new – server roles

Windows 7 Professional (x64) Service Pack 1 (build 7601)
Install Language: English (United States)
System Locale: English (United States)


System Model

DELL Inc. Studio XPS 435T/9000 00
Enclosure Type: Desktop


Processor

3.20 gigahertz Intel Core i7 960
64 kilobyte primary memory cache
256 kilobyte secondary memory cache
8192 kilobyte tertiary memory cache
64-bit ready
Multi-core (4 total)
Hyper-threaded (8 total)

Main Circuit Board

Board: DELL Inc. 0X501H A03
Serial Number: ..CN6970202S0926.
Bus Clock: 133 megahertz
BIOS: DELL INC. A16 02/04/2010

Memory Modules
8184 Megabytes Usable Installed Memory

Slot 'DIMM0' has 4096 MB
Slot 'DIMM1' has 4096 MB
Slot 'DIMM2' has 4096 MB
Slot 'DIMM3' has 4096 MB
Slot 'DIMM4' has 4096 MB
Slot 'DIMM5' has 4096 MB