Windows Vista and Windows 7

• 1). Click the "Start" button, type "System" in the search box and press "Enter."
  
  
• 2). Click the "System Summary" option in the left navigation pane.
  
  
• 3). Find "System Type" in the right informational window and make note of your system's edition.
  
  

Windows XP

• 1). Click the "Start" button and choose "Run."
  
  
• 2). Type in "sysdm.cpl" in the search box.
  
  
• 3). Click the "General" tab. If Windows lists "X64 Edition," it is a 64-bit version of Windows, if it does not list an edition, it is a X86 32-bit edition.