If you are using Windows:

If you are using a Mac:

• Right click your "Computer" or "My Computer" desktop icon and select Properties.
• Your OS will be displayed on the top line.
  

  Windows 7, Vista, Server 2008

  

  XP, 2000, Server 2003, etc.

• Note: A bug in some Windows 64-bit operating systems prevents the system from displaying what OS you have.

• Click the Apple icon in the top left corner.
• Select the "About This Mac" menu item. Your OS is displayed on the splash screen.
  

  Mac OS X 10.4, 10.5 & 10.6