RAM Under-rated

[static_x]

Hi,
Assembled my new system with:

AMD Phenom II X4 940
Gigabyte GA MA790GP - UD4H
Corsair 800Mhz 2GBx2 RAM Modules

My system is showing only 2.75 gb of RAM. I understand that OS being 32bit the RAM showed is less than 4 GB. But my office PC (HP System - using E7400+4gb RAM) shows 3.31 GB of RAM. I cant understand why there is such difference of RAM Capacity? Does it depends on the Processor and MObO used?

Also, if i install 64bit XP then do I've to install all my softwares again i mean will the current softwares which run on this 32bit sys will work on the 64bit machine?

[desiibond]

dude. if you haven't installed any GPU, onboard GPU will take 512MB of RAM.

[Arnab boss]

I think there was a similar probs with ram in this forum...' it was the os I mean the win xp 32 bit that was causing it....?
Reinstall the winxp and then c it..'

[Krow]

I have the same Board and Proc. RAM in XP 32 bit is 2.75 GB! Try GPU-Z and u'll c that u have 640MB VRAM. 512 MB is shared minus the GFX Card. If u have a GFX card installed, then its a prob. With integrated gfx, its not.