Today, I volunteered to help a new friend who could not use her Mac laptop. She could get the gray Apple icon screen on powering up, but eventually it turned to a blank blue screen with no icons or dock or hard drive image. She mentioned at one point that she had been told by the Apple Genius store that her hard drive was full, and that she needed to hook it up with another Mac in Target Mode to access her hard drive to clean off some of the files.
I tried the option, command, P, R sequence of keys to execute a PRAM boot sequence. This did not help. So with a suggestion from my husband we tried the Safe Boot Mode. To boot a Mac in Safe Mode - power up the computer, after the first tone sound, hold down the Shift key and release once the gray screen and spinning wheel and progress bar appear.
This worked and we were able to see the friend's hard drive, dock and files on the desktop. From that point, I realized that she had been trying to remove some of her photos from iPhoto application to make room on her hard drive. There were a number of things that she did that actually caused the hard drive to fill up. She kept saying that she had multiple copies of each photo in iPhoto and could not seem to get rid of them.
This is the scenario that I believe caused this duplication:
She thought she could drag the photos from iPhoto application to the trash can to get rid of them. She did not realize that the photos were being copied instead of deleted from the iPhoto library. Every time she dragged a photo out to the trash, it was duplicating the photo instead of deleting it. She did this a couple of times, and as she did this, more duplicates of the each of her photos were placed into the trash. She was compounding the hard drive space problem without realizing it.
I deleted the trash can which got rid of the duplicates there, but in exploring her hard drive, realized that she had also possibly dropped these same files she was trying to delete into her home folder and had another two sets of duplicated photos.
Once I found these and selected them and put them into the trash and also emptied the trash, her hard drive space was back. Now, she is able to use her Mac again.
There are several things that can be learned from this:
(1) A file is still on your hard drive, present in your trash can, until you actually empty the trash.
(2) You cannot delete photos from iPhoto by dragging them to the trash. To delete a photo in your iPhoto library, you need to run iPhoto, select the photo or photos to delete, and then hit the Delete key. The photos then are moved into the Trash can in iPhoto application. You must also empty the Trash in iPhoto for these to be totally removed.
Additional notes added 4/2/2012:
(3) Also, note that selecting an album and hitting the delete key does NOT really delete all the photos in the album (as these are really only alias or pointers to the real photos). Remember to delete photos, do so by selecting photos icon from the left hand column and then deleting each photo individually or delete multiples that are selected from the main window on the right.
(4) There are a number of short cuts that you can use to select multiple photos at once to delete. Using cmd A to select all. Dragging the cursor to select multiple photos within the main window. Also adjusting the size of the photos using the "zoom bar" at the lower left of iPhoto will allow you to see more photos at once, thus you can drag select more at once to select for deletion. Selecting one photo while holding down the shift key, you can select other photos by clicking on them and holding the cmd key down. This will allow you to select photos that are not easily in a group.