Thankyou all for the advice
repeatedly edited: The bulk is trivial but time consuming to replace - mp3s and films. There are some documents and files that I really do need to keep, but nothing really justifying data recovery prices.

I might try the freezer thing first; since I have all the necessary kit already, and that one drive is already borked. Failing that, I'll escalate to risking the good drive and swapout the boards; as soon as I get a set of Torx screwdrivers.

(sorry I'm lagging a bit, 300Mb+ of windows updates are hogging my connection).

update: Still waiting for vista to finish patching - it's nearly eaten the whole 20Gb by itself (Bloatware indeed). I can't do anything until it finishes, the two drives in question still sitting on the bench.
(The Incredible Sulk Finally remembered his password on, Thu 1 Oct 2009, 0:45, 1 reply)

Any sort of sound or vibration coming out of it?
If you can hear it click as it fails to spin up, it's not the logic board. If on the other hand it does a brick impression when you turn on the computer, try the logic board swap first.

EDIT: Also, if/when you're swapping the logic board, be careful with the ribbon connector (if it has one). Make sure you very gently push the tab on the connector fully out, and the cable should slide off very easily.
(rpozz, Thu 1 Oct 2009, 0:51, closed)