Win XP RAM question

[espguitarguy232]

So i Recently installed 4 gigs of OCZ reaper DDR2 800 RAM and i was wondering why XP only shows 2.75 instead of more in the range of 3.25-3.5. I had 2 gigs of another type of OCZ RAM and it showed all 2 gigs. What I am trying to figure out is in my setup, what is taking up the memory. I have a 650i Ultra mobo, 8800gts 512, onboard realtek sound, onboard network, and thats about it that may affect RAM usage. So what I was hoping is if any of you guys can explain where it is going in my setup. Thanks

 

[treefrog07]

MS x86(32-bit) OSes (XP, vista, and Win7) can only see and use about 3.5 GB of memory. Memory with first priority is CPU, then GPU, then RAM. It looks like you have about .75 GB of memory installed in your CPU and GPU, so the OS can only see and use the 2.75GB it showed you.

 

[espguitarguy232]

So what decides how that is allocated? Is it decided by the motherboard?

 

[espguitarguy232]

Bump. In my research I have noticed that people with nvidia's nforce chipset tend to have the 2.75 gigs of space available, which was the same for my brother's 780i that I got the ram from. CPU-Z reports all 4096 mb. Is the nforce chipset and the components associated with mobos with this chipset memory hogs?