My grandfather's PC won't start up. It's a HP 6355 or whatever. Anyway, the hard drive won't boot. When it starts up, it makes this constant clicking noise, like it's trying to find something. Actually, yea, it's trying to find Win98, but after a few secs, the monitor says "No Operating System Found". HP Customer Support is charging $25 per call for this particular model so, that's out of the question. Anybody have any ideas? It's Western Digital regular IDE drive. Could it be dirty or something's stuck inside? Help.