how stock photos on external hard drive

What is your Aperture Version and Mac OS? Your signature says "PowerBook G4", but your question MacBook Pro?

o.k., I just wanted to be sure of your Aperture version, for I have not worked with Aperture 2 for a long time.

I want keep my aperture library on my macBookPro and when import photos copy it on external hard drive. This way i let my MacBookPro hard drive free. How can i do it?

I think, what you should go for is a referenced Aperture library. Keep your Library on your MacBookPro, and when you import images to Aperture relocate the Master image files to your external volume. You should set your Aperture Preferences to build Previews of all images - set the Preview size to the size of your screen (this is set in the Preference panel, Previews tab). This way you can use all your images in the screensaver and in the Media Browser, so that you can use them in other iLife and iWorks apps, even if your external disk is not available. You will be able to browse and tag the images in Aperture, but to be able to edit the images, you will have to connect the volume with the master image files.

See: Working with Referenced Images in the User Manual:

To relocate master image files launch Aperture and select the images in the browser; then select:

File -> Relocate Master(s)

This will open a FileChooser panel; select a folder where you want to store your masters.

Make sure your external volume is formatted "MacOS Extended" before you move any master image files there, otherwise you may run into problems with ambigious filenames.

I like to keep the most current projects I am currently working on as managed masters on my MBP, and when I am finished with the Books and Slideshows, I relocate the masters to my external Media Drive. Post back, if you have more questions.

Regards

Léonie