There are many different versions of Windows that your PC may be running. This is a short guide to determining which version you are using.
Windows 8 has a hidden start button. When clicked it opens tiles.
Windows 7 has a start orb and a blue taskbar. The start menu also has a search box in it.
Windows Vista has a start orb and a black task bar.
Windows XP has a green start button and blue task bar.