I purchased a Lenovo G570 (Model Name: 20079) and it has a Core i3 2350M and 4GB RAM.
I installed windows XP (32-bit) and when I checked the task manager/properties of my computer; it shows only 3GB of RAM. I have also tried another OS - I installed puppy linux(32-bit), and checked top; it shows 3GB of total memory.
Why is only 3GB of the 4GB of installed memory recognized by the OS? Why doesn't the OS recognize the full 4 GB of memory?
Windows XP, being a 32 bit OS can only address a maximum of 4 GB ram, and some of this addressing space is used for video or other system needs. As a result, depending on the system, BIOS, Video subsystem, Windows will report typically between 3GB and 3.5GB of RAM (and sometimes slightly less than 3GB) out of the 4GB physically installed.
To recognize and access the full memory installed, you will need a 64 bit OS.