First, locate the My Computer icon by selecting the Start Button located in the lower left hand corner of your screen.  Left click one time on this button to select it.

When you select the Start Button the Start Menu will appear.  On this menu you should see a icon call My Computer.  RIGHT click on this item to activate another menu. If you can not find the My Computer Icon in this menu or do not have this menu, you may be able to find the My Computer Icon on your desktop.  

When you right click on the My Computer icon a submenu will appear.  The last item is called Properties.  LEFT click on this option to access the System Properties page.

 

When the System Property Window opens you will see a section labeled System.  In this section you can identify the Operating System your computer is running.  In the image below, we see the Operating System is Windows XP.