That's no fun... but yeah, a harddrive can die from about a thousand different causes, and not all of them make noise or give warnings. Two main distinctions are if the drive's electronics fail, or if the mechanical stuff fails. The electronics _should_ outlast the mechanical bits, but when they do die (from a short or surge usually) it's sudden, with no noise and no warning. The more common thing is mechanical failure, and that usually does give warnings as it gets worse. Often funny noises, but more reliable is to check error rates that increase... that'll show up as it just acting "slower" for a while. If you can, use SMART monitoring tools. I don't know where/what that would be on a mac, but the drives have internal self-test and error monitoring firmware, and you can put software on your computer that will talk with that, and notice when certain conditions are increasing too fast (so-called "pre-fail attributes") and give you some advanced warning for a dieing drive.
As for the install discs... that should have nothing to do with the hard drive. Check them for fingerprints and scratches? :-)
