Windows 7 - 4GB of RAM installed only showing 3GB

costello, you're using the 64 bits version?
post more hardware information and we'll try to help

solved i formated the windows..

sori to interrupt here,when this happen to my wife Aspire 4520,i'm update my bios and it works!i'm x sure if it work to u.

Do you have an integrated video card? I doubt it would use up 1gb of RAM but many integrated video cards like the ATI Radeon Xpress do not have discrete VRAM. Instead, they rely on your RAM to perform that role. Some can even be adjusted how much memory to allocate to it. I doubt that is your problem though because 1 GB would be an awful lot for an integrated graphics card, but technology is advancing. We have 2 GB discrete cards, so I suppose a 1 GB integrated would be possible. Just unlikely.

Hi Adam.
This problem looks to be far mor complicate than it seems!
I used windos 7 32 bits on a Acer Aspire 5630 and I had 2GB and EVERYTHING could see that ram, the HARDWARE RESERVED MEMORY was only 2MB! I put more ram so I had 3GB and all system could see all ram the HARDWARE RESERVED MEMORY was the same 2MB! To use 4GB on my Acer I did a fresh install of windos 7 64 bits! I updated the Bios, chipset, graphic card, etc... Now everything see 4GB but windos 7 64 bits could only use 3GB! The HARDWARE RESERVED MEMORY is Now 1026MB!! It did pass from 2MB to 1026MB! I checked to test with 3GB on 64 bits and in that case it show the HARDWARE RESERVED MEMORY 2MB!?! So I put the 4GB again and the HARDWARE RESERVED MEMORY is again 1026MB! On the manual of my Acer Aspire it say that it can use 4GB! To the record, this notebook is runing the windows 7 ultimate 64 bits with no problem about drivers the only probem is the HARDWARE RESERVED MEMORY issue. Thanks in advance to someone could get a shot out of the usualy explanations.