applications

1.Click Start, and then click Run.
2.Type sysdm.cpl, and then click OK.
3.Click the General tab. The operating system is displayed as follows:
         a.For a 64-bit version operating system: Windows XP Professional x64 Edition Version < Year>
            appears under System.
         b. For a 32-bit version operating system: Windows XP Professional Version <Year> appears under
             System

Note <Year> is a placeholder for a year.

Basically 32bit will look like this

System:
     Microsoft Windows XP
     Profesional
     Version 2002

And 64bit XP will look like this.

System
      Microsoft Wondows XP
      Professional
      2002