windows display 2.5 GB of ram instead of 3.5gb

i am using windows 7 32bit and in my computer properties it said "Installed memory ram: 4.0GB (2.5 gb ram useable)"

and in the resource manager



i understand that 32bit OS can only get 3.5GB ram at max but why i only have 2.5GB ram? Does this have anything to do with my VGA 5870 which have 1GB ram?

Hi Mano
I am sorry to say but that is about the limit of what 32bit Windows can see, If you would like to use your full 4.0gb ram then I would suggest that you upgrade to Windows 7 64bit
Thanks Ashley
Edit bellow
If that is not the case then I had a computer that would ony see 2.0gb, Try seeing if your motherbored software/BIOS is up to date and that your motherbored can support 4.0gb ram

You've got a lot allocated to hardware. 1500+MB. Have you gone into the BIOS to see how the memory is being used/shared?

what should i look for in the bios?

update: i installed windows 7 64bit and indeed i see all of my 4gb are used. So it is confirm that the 32bit only let my use 2.5gb ram. However as the matter of curiosity, why 32bit OS only let me have 2.5gb ram instead of 3.5gb?

Because your video cards 1 gig of memory is mapped into the 4 gig address space you are already down to 3 gigs. Then you subtract any other address space used by hardware. When you switch to 64 bit windows the video cards memory can be mapped in the address space above what is reserved for your RAM. There is no 4 gig ceiling to hit. Windows has room to keep track of it all.