Windows Vista: Click Start/Vista icon, right click on Computer. Under the System category you will find the amount of RAM memory.
Windows XP: Click Start, right click on My Computer, then left click on Properties. Click on the General tab you will find RAM near the bottom of this page under “computer”.
Windows 7: Open System by clicking the Start button, right-clicking Computer, and then clicking Properties.In the System section, next to Installed memory (RAM), you can see the amount of RAM your computer has.
Macintosh: At your desktop, click on the “apple” icon and drag to About This Mac. The number next to “Total Memory” is what you are looking for.