I recently tried installing an OS from two gray disks, one for applications and the other for the OS. I recently installed a new hard drive and needed to reinstall, couldn't find my disks so bought two cheap ones off of eBay, bad idea, I know. I got an error like "This OS cannot run on this" it wasn't exactly like that, but had the same meaning. Found out that I need system specific working OS, so will buying a copy of ML work on my? Here are the specs: MB Pro 5.5 Intel Core 2 Duo 2.26 GHZ 4GB Have no backups, so starting from fresh. Will a copy of ML from Apple work?