It means that your processor can handle 64-bit Windows 7 or Vista. In 64-bit architecture you can use more than 4gb of ram. In 32-bit the OS will only recognize just over 3gb of ram even if you have more installed. I have 3gb of ram in my laptop and still run 64-bit Windows 7 because it is faster and more secure than 32-bit Windows. 64-bit is still relatively new, so if you do go to 64-bit make sure that there are drivers available for your devices before you adventure into it. Also, some older apps will not run on 64-bit Windows.