My girlfriend brings me a Western Digital 40g and wants to know if I can recover some data from it for a fellow teacher/friend of hers.  I said sure.

Initially the problem was the drive making horrible noises and clicking, not allowing them to boot.

I get it here and plug it in and it works fine so I burn the requested data to a DVD and they're all set.  So I think I'll keep the hard drive myself as an extra since I can't figure out what they're talking about and they had already bought a new one.  The hard drive wasn't half full.

Then it starts....  the clicking and sputtering...  worst ever, never heard anything like it.

So I take the hard drive out and disassemble it for whatever reason (I'm not sure) and put it back together.  It was still clicking and going ape shit so I then took it into my hallway PC and mounted it vertically and it's been running noiselessly and perfect ever since.

I'm currently running a list of HD diagnostics from DOS to try to determine what's up.

Any ideas?

Sounds like the heads aren't floating right.  In normal operation, the hard drive heads ride on a cushion of air created by the drive as it spins.  It sounds like the air cushion isn't counteracting gravity anymore.  Mounting it vertically must be helping the heads not crash against the platters.