Your computer operating system, whether it's a Windows or Mac computer system, is either 32-bit or 64-bit.
The following instructions are for Windows Vista and Window 7. For all other versions of Windows such as Windows XP and so on please visit the following page from Microsoft for further details on how to determine if you're running a 32-bit or 64-bit version of Windows.
On Windows Vista or Windows 7, to find out if you have a 32-bit or 64-bit computer, click on the Windows icon called "Start" on the bottom left side of your screen, then click on Control Panel in the list.
In the new pop-up window click System and Security, then click System.
Under the header System, you will find whether your system is 32-bit or 64-bit under System Type.
To find out this information, click on the Apple icon at the top left side of your screen, click on About This Mac in the list.
In the new pop-up window click More info.
Under the header Hardware you will find your Processor Name.
Compare your Processor Name to information below to determine whether your Mac has a 32-bit or 64-bit processor.