Hi! It sounds like you've diagnosed this correctly. One way to rule out the rest of the computer is to connect to another Apple computer via Firewire and boot from that computer's hard drive in target mode. If the laptop runs fine using that computer's hard drive and doesn't exhibit any of the same symptoms, then you know the laptop is fine and the hard drive is bad. If the reverse is true and you do notice the same symptoms, then it is possible there are some other hardware issues with the laptop. But again, sounds like if you swap the drive you'll be in good shape. Good luck!