Select one contact, scroll to the last contact and shift-click on it. That should select EVERYTHING between the first and the last–so be careful. Then hit the DELETE key on your keyboard. If there are contacts you do not wish to delete, simply Shift-click from the first one you want to eliminate to the last one before the contact you want to keep. Then skip that one and begin again. Might take a little thought and a little time, but it can be done.