I just replaced the hard drive successfully. That really wasn't that bad. I am happy to report that my quadra is now running perfectly. No more problems at boot-up, or loud noises from inside of the computer. It is working flawlessly, even the cd caddy drive is working. So my quadra 610 problems are over (for now). Next step will be to connect it to the internet and set up file sharing. Anyways, the hard drive that I ordered came with os 8.1. Should I keep that or downgrade to 7.6.1? I really want to know if there will be a difference in performance between the two. Thanks to everyone who helped me out.