K9A Platinum and 4GB DDR2-800

Question

I'm a major MSI fan and have been for a long time. My computers (even my customer's) are MSI boards.
Recently, I upgraded my motherboard, ram and processor to the new AM2 core (ok, not really new, but w/e). I have the following items:
MSI K9A Platinum
4GB DDR2 800 (2x2GB) G.Skill 5-5-5-15
Athlon X2 5200+ Windsor 65w w/2x1MB cache
2x ATI Radeon x1650 256 DDR2 (Crossfire'd)
1x 200GB SATA2
1x 300GB SATA2
2x 500GB SATA2
My previous system had:
MSI K8N Neo-4F
4x 1GB Kingston DDR 400
Athlon X2 4800+
Ok. So heres my problem:
I installed each 2GB stick into slot 1 to verify they work and I got all 2GB. Shut down and installed each 2GB at each channel (DIMM1 and DIMM3) and BIOS reports 2544MB total. I look in BIOS and it says Physical Memory = 4096MB, Usable Memory = 2544MB. (This is before I even installed windows.) So, I tried to see if windows would report differently and after installing, it reported the same 2.48GB of ram. Now I know that Windows 32-bit can only go up to 3.2GB and I have no problem with that. My previous setup reported all 4GB of ram... so whats different about this board that it doesn't use all the memory available?
If this is an issue with the Processor, then let me know. I paid for 4GB, not 2.5GB. I expected at most 3.2GB.
And no. I won't go Vista. And Windows x64 has little to no support for a lot of what I do/have. So I won't use it either.
Thanks for your help in advance.

Answer 1

@ BOSSKILLER:
I've done the single and dual vga test. I even placed the ram in single channel mode and it did the same.
@ Bas:
Its default. I'll paste it here.
Code: [Select]
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect /usepmtimer
Thanks for your responses so far.
Just for record, here is the RAM information taken from PC Wizard 2007 (From the makers of CPU-Z):
FYI: In the ram size, 2 ranks, 8 banks means its a double sided chip. 2 sides (1 rank per side), 8 chips (1 bank per chip) per side.
Code: [Select]
Information SPD EEPROM (DIMM0) :
Manufacturer : G Skill
Part Number : F2-6400CL5-2GBPQ
Serial Number : Unspecified
Type : DDR2-SDRAM PC2-6400 (399 MHz)
Format : Regular UDIMM (133.35 x 3)
Size : 2048 MB (2 ranks, 8 banks)
Module Buffered : No
Module Registered : No
Module EPP : No
Width : 64-bit
Error Correction Capability : No
Max. Burst Length : 0
Refresh : Reduced (.5x)7.8 µs, Self Refresh
Voltage : SSTL 1.8v
Prefetch Buffer : 4-bit
Manufacture : Week 0 of 2000
Supported Frequencies : 266 MHz, 400 MHz
CAS Latency (tCL) : 4 clocks @266 MHz, 5 clocks @400 MHz
RAS to CAS (tRCD) : 4 clocks @266 MHz, 5 clocks @400 MHz
RAS Precharge (tRP) : 4 clocks @266 MHz, 5 clocks @400 MHz
Cycle Time (tRAS) : 10 clocks @266 MHz, 15 clocks @400 MHz
Min TRC : 16 clocks @266 MHz, 23 clocks @400 MHz