Microsoft Windows XP was available in Home and Professional versions, with the Home edition available as 32-bit only. The Professional edition was available as either 32-bit or 64-bit. In order to run the Windows XP Professional 64-bit version, the computer's processor must also be 64-bit, meaning it can process twice as much data in a single operation as a 32-bit processor. This allows data to be processed faster, and more RAM to be addressed, removing the four gigabyte memory limit faced by 32-bit operating systems. To check if your copy of Windows XP is 32-bit or 64-bit you can use the Windows Control Panel.
Click on the Windows "Start" button and select "Control Panel" from the Windows "Start" menu.
Double-click on the "System" icon to open the system properties dialog box.
Click on the "General" tab and look under the "System" section. If the operating system is listed as "Windows XP Professional x64 Edition" or "Windows XP Professional 64-bit Edition" the operating system is 64-bit. If the operating system is listed as "Windows XP Professional Version," the operating system is 32-bit.