This is taskmanager of my server, you can bring task manager by right clik at your task bar(at clock display) then klik task manager.

look at below at poit I had mark underline.

How you know if your computer is need more ram?

1. Check Physical Memory Information at Available info,as you see phisical ram 4192564K(4Gb)

but available 614600K(or just left 600MB) ,it's mean all most phisical ram Block is used. if you check yours still big, may be half of your phisical size it's mean it's still safe.

2. Check Commit Charge at Peak Section. as you see as this example peak is reach 5407592K(or amost 5GB) this information the peak of memory which loaded at your computer.

so if you had phisical ram 4GB but you computer loaded 5GB it's mean you need more RAM.

but if you peak just bellow your phisical RAM you don't need more RAM.

Oke.. with this example we can learn that this server need more RAM :)