Posted 28 September 2011 - 01:54 PM
Simply put...available memory is what is available to Windows at any given moment...this memory is not being used by other parts of the system. While installed memory is just that...the total RAM installed in the system.
The two will never equal, since a small portion of whatever is installed...is used by Windows and onboard video.
This is further complicated by the O/S used. Windows 32-bit can only use 3-3.5 or so of any amount of RAM installed, so that will always be the max reflected for 32-bit Windows.
A 64-bit O/S can use larger amounts of RAM, so that number could increase...but it will never be the total RAM installed.
In other words...those figures reported by Task Manager...are, IMO, meaningless to the average user, since the only number that such users really need to know is how much RAM is installed.