Umm, we have absolutely no idea?
If you would provide more information we might be able to help. What OS are you running? 32-bit or 64-bit? What hardware do you have? Where do you see htat 2.44GB is available?
I would guess that you are running a 32-bit OS, which limits your memory to 3 GB, and that you are using on-board graphics, which is taking up part of your memory. But that's just a guess.