How to switch between MAC OS X (Leopard) & Windows XP on the dual boot computers?

How to switch between MAC OS X (Leopard) & Windows XP on the dual boot computers?

Dual Boot Computers

Upon startup/restart, a menu will appear which will allow you to select an operating system. You have 20 seconds to select an operating system, otherwise the default will load. Use the arrow & enter keys to select an operating system.
Note:  iMacs are no longer dual boot except for the Wong classroom computers which are slated for replacement by windows only machines.  iMacs run OSX only.