Does sound like a motherboard fault to me if you have tried two different HDD's and they both do exactly the same thing, especially with the odd boot message you are getting.
Might be a very long shot, as I've never had (or heard of) a faulty one, but have you tried a different IDE lead? Like I said, a very long shot, but worth a go before spending any money!
You could also try swapping the boot sequence so that CD is first and HDD is second - it won't do any harm and might give your HDD time to spin up if that is actually the problem, tho I somehow doubt it, you can never rule anything out with computers! I'm rather fond of saying that for something which works entirely on logic, computers are remarkably illogical sometimes!!
I can't remember if you said now, but is this a problem that has just appeared overnight for no reason, or has the PC always been like this?
Matt