How Do I Tell a 32 or 64 Bit on Windows XP Pro?
Determining whether or not your Windows XP Pro computer has a 32- or 64-bit version of Windows XP is helpful if you are considering buying software that is optimized for 64-bit processors, or if you are trying to find the easiest way to upgrade from Windows XP to a newer version, like Windows Vista or Windows 7. For example, if you are running a 64-bit version of Windows XP Pro, you cannot upgrade to a 32-bit version of Windows Vista or 7 without reinstalling the operating system.
XP Pro Version via System Properties
Open the "Start" menu by clicking on it, and then select "Run."
Type "sysdm.cpl" to open the System Properties control panel, and press the "Enter" key or click "OK."
Click the "General" tab.
Review the operating system information displayed. The 32-bit version of Windows XP Pro is identified as "Windows XP Professional Version YYYY," where "YYYY" is replaced with the version's release year. Windows XP Pro 64-bit is identified as "Windows XP Professional x64 Edition Version YYYY."
Click "OK" or "Cancel" to close the detail window once you determine the version of Windows XP Pro used on your computer.
XP Pro Version via System Information
Open the "Start" menu and click on "Run."
Type "winmsd.exe" in the Run window and press "Enter" or click "OK."
Select "System Summary" to view detailed computer information, and then click on "Processor" under the "Item" heading.
Take note of the processor type displayed. If the name of the processor starts with x86, the computer is running a 32-bit version of Windows XP Pro. If the name starts with ia64 or AMD64, the computer is running a 64-bit version of Windows XP.
Click "OK" to close all of the windows opened after determining the version of Windows XP Pro installed on the computer.