MAC OS

First, make sure that your external hard drive is USB capable. If it uses firewire, then that might be the issue. If it is USB capable, then plug it into the power book. Wait at the most 1 minute for it to recognize the external hard drive. If it does not appear on the screen, you may want to try and plug it in on a second computer. If it doesn't show up on a second computer, the hard drive may have a problem/bug. If it does show up, then drag the selected files onto the hard drive. If it says you can't, then there probably isn't enough room on the hard drive to store the files. That is about all that can be explained to you from the information given.

To take a screen shot with Mac OS X hold down the Command (cmd) key and the shift key and either the number 3 to take a shot of the whole screen or number 4 to change your pointer to cross-hairs that can be dragged across a section of the screen to capture just tat part. With the cmd+shift+4 option you can put your pointer over a window and press the space bar to capture that window,

In the Utilities folder which is in the Applications folder is software called Grab which does the same thing but also allows for a delayed capture which gives you ten seconds to arrange your screen before taking the shot.