Simply select all your images (CTRL a) and then hit Delete.
You'll get a dialog asking if you also want to remove the photos from your hard drive. Assuming you want to keep the photos, do not check the box.
The Catalog will be cleared, but your photo's will still be on your hard drive.
Remember, your photos are not in Starter Edition. Starter Edition is simply cataloging what is on your hard drive. If that's not making sense, read through:
It's not exactly on this topic, but will provide some interesting info.