Q. I don't know whether my computer is 64-bit or 32-bit.
A. In Windows 7, right-click on Start < Computer and left-click on Properties (R) to display the system.
Under "System type," you will see either 32-bit operating system or 64-bit operating system, so you can check which OS you are using.

Q. What are 32-bit and 64-bit applications?
A. Some applications, such as Internet Explorer 8, Word, Excel, and PowerPoint, exist in two types: 32-bit and 64-bit versions.
You can check whether the application you are using is a 32-bit version or a 64-bit version by referring to the version information in Help.