Gigabyte GA-K8VM800M RAM issue.. only seeing half of it

Acer Aspire T135
Ram is two DDR 400 1GB PC3200.
MB is Gigabyte GA-K8VM800M
AMD Sempron 3300+ processor
NVIDIA GeForce 7300 GT 512MB RAM (Omega 2.169.21 driver)
BIOS R01-B4 (10/17/2005)

I installed the RAM upgrade late June. At that time, I saw 2GB available in my properties. I don't know when it changed, but now I only see 1GB. Both sticks will boot the PC independently, from either slot, so they are good. Everest sees only one, MemTestPro sees only one, but I tried an online scan that showed two.

The thing that changed between installing the RAM and now is that I upgraded my power supply to 500W so I could use my new nVidia card. Did that change something, so only one pipe works at a time?

I see no where to change whether any of my RAM is shared with that video card. Shouldn't there be an option in CMOS?

I'm completely baffled, and about ready to just upgrade the MoBo to something faster. Before I do that I want to know if this situation can be remedied.

Sorry, it is XP Home Edition, Service Pack 3.

Here is all my boot.ini has to say.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /fastdetect