how do I copy photos over from iphoto to an external hard drive

depends on what you want to do

If you want to save your photos then you do it the same as you always do to access photos - select them in iPhoto and export (file menu ==> export) to the desired location (see this user tip for details on exporting)

If you want to backup your iPhoto library onto an external drive then you simpoly drag it intact as a single entity to the EHD

If you want to run iPhoto off of the external drive after moving your iPhoto library you depress the opotion key, launch iPhoto and use the select libreary window to select the new location - fully test it and delete the one on the intrnal drive

And verify that yoru backup is backing up your external drive if your photos have any value to you

LN

If you're wanting to just backup the original image files be sure to select Kind = Original when you export out of iPhoto. You can also select the option Subfolder = Event to get each Event's original files exported to a folder with that events name:

But then if you're wanting to operate your library from the EHD then copy it over and open as Larry described.

OT