RE: Missing 1GB RAM, where is it?

I'm little confused about amount of RAM memory in my computer and I can't figure out where disappear about 1GB memory. I need yours help to explain this, because i can't sleep :). Here is background:

I've plugged into my computer 2x2GB RAM. In BIOS screen i see:

Amount of available RAM: 4096MB

so BIOS recognizes all 4GB, but my OS(32bit)

Just a thought - lower end graphic cards use system RAM as their own dont they. Adrian Cornish