I went through the same thing not too long ago with a 160Gb drive and 110GB of MP3's (all legal) and lots of documents. It was just corruption and not the hardware failure though. I spent the better part of 40-50 hours using different recovery software and was finally able to get about 95% of the data off the drive. I consider myself lucky at this point and have a complete backup of my mp3's on a spare drive.
BTW, I have an old Toshiba Libretto (Pentium 233/64MB ram) that I use quite often for a variety of tasks along with a Pentium II 433 that I use for recording off my board (using Audacity). Just becuase the hardware is older doesn't mean it's not still useful. The only reason I've seen recently to upgrade to the fastest and greatest is because the new games require it (check out the requirements for Doom 3). Some people doing rendering and heavy video/graphics editing might use that power but the average user ends up with a PC that just waits faster.
I'm happy you were able to find a power supply. I've had good luck finding obscure parts at Computer Renaissance (it's a franchise store).
As for the failing hard drive, you can try tapping it while it's spinning on your hand if it's not spinning up, but when it starts clicking it's usually the head motor/hardware driver having problems and not the platters failing to spin. Most of the remedies you see on the internet (including freezing) are geared towards the platters not spinning. A long shot if you have an identical drive is replacing the board on the bottom of the drive with one from another drive (same manufacturer and model). Only takes a few minutes and it 'might' fix the problem long enough to recover your data. Of course there are data recovery services but they're usually quite expensive and usually charge by the amount of data to be recovered.
