Okay, the problem is the PC turns on but the red light (by the
drum/tube type
icon on the case) stays on and doesn't do much else. The computer
hums but
doesn't post, no drives can be accessed, nothing comes up on the
screen (except
a "no input" message".

That red light means the hard drive is being accessed.

Open the PC and unplug the ribbon cable from the hard drive (and
possibly CDRom) and see if she boots up.

Could really be a million different things though.