Aperture 1.5 default location for all your master images is located in the Library which is in the Picture folder of your operating system's Home directory. When you open Aperture for the first time you will want to change the default location of the Library to an external or an internal drive other than the hard drive where the operating system is located. Here's how:
1. Mouse open Aperture's Preferences window by using the menu Aperture>Preferences or using the keyboard shortcut of Command ,
2. Once the Preferences window is open spot the Library Location and click the Set button immediately under it.

3. Navigate to the new location where you want the Library Location to be like your external drive or if you have more than one internal drive pick it.
4. Now click Select.
5. Restart Aperture in order for Aperture to recognize the new Library location.
victor m maldonado