twaddle
I have no idea what the reason is off the top of my head but I don't agree with the above answers as I'm assuming you mean that it shows as 11GB under 'computer/properties' the display window that shows basic information about your computer.
So surely how much of that RAM is being used has nothing to do it skycraft Windows is reporting the RAM is has available to use, not how much is physically present in the system.
The task manager will tell you how much is being used but the, 'computer properties' is telling how much is installed and NOT how much is being used.
I had a problem where I had 12GB but windows was only showing I had 6GB, turned out I just hadn't pushed the new sticks in hard enough. It's very odd that it would show as being 1Gb less though as RAM these days is almost never in sticks of less than 2GB.
Steve
Depends on the version of Windows. They changed it to show installed RAM, precisely because people were getting confused. Used to show accessible RAM. I don't remember when they changed it.
At any rate if you think it is an issue of the RAM not being present you can check two things:
1) The BIOS. I'll report what is physically present in the system.
2) HWiNFO64. It'll again give you a report of what is physically in the system, including what sticks are in what slot and all that.
You can also have a look at Resource Monitor (an included windows tool) to see distribution. It'll show you a RAM breakdown, including hardware reserved memory. The amount can vary greatly depending on how much memory you have installed, what motherboard you have and what BIOS version (since that affects memory control), and what peripherals are in use. I've seen it be 0MB on some systems, and as high as 1.25GB on a 32-bit system at work with some hardware video capture cards. It is 31MB on my system at home, which the motherboard documentations notes it will be.
Given that he says his BIOS claims 12GB is installed, it is not likely to be a stick being loose, or other physical failure. The BIOS wouldn't see it in that case.