Alt-Tab is your friend...

The Alt-Tab key combination is a powerful Windows tool. It toggles you between applications, saving you the work of minimizing and restoring windows to switch between running applications.

You hold down the Alt key (located next to the space bar) and press the Tab key repeatedly to move between the currently running applications.

The thing which is not immediately evident is that Alt-Tab will toggle immediately between the two most recently used currently running applications. So, for example, if you need to switch back and forth between Microsoft Word and Internet Explorer, hitting Alt-Tab moves you from one program to the other, even if several other programs are also currently running. in other words, you don't need to look at the screen choices of Alt-Tab when toggling between two applications. This can be a considerable timesaver if you need to cut and paste many items, alternately from one program to another.