I have built dozens, most from parts that I got from the "defective" parts bin at work when I was at IBM. The main problem with the "swap till you drop" maintenance philosophy is you condemn a lot of good parts. When I was building those machines the only part you couldn't get was the case because it had a serial number so I built "woodies".
I always had a woodie on my desk at work, the parts room inventory machine was a woodie as were the servers for our dial up access to the network.
When I started using a machine at home in the living room my wife said it had to "fit in" so everything but the monitor and keyboard was red oak.

I still have a woodie in the garage as an MP3 player for the pool bar and another one in my computer room/shop/den that streams TV from the Replay and one in the entertainment center in the living room as another MP3 player.

I am getting parts on the internet these days, usually from surplus places like Gearxs or PCSurplusonline. The only machines I have actually bought assembled were the laptop that I use as a server and this 2.4g Compaq I got from Gearxs, mostly because it came with an XP Pro license for $90. That is less than XP costs. It is plenty fast enough for me.
Hard drives are just a consumable commodity that I get from whomever has one on sale. Western Digital is the only one I will never buy again. 90% of the bad drives I have accumulated over the years are W/D Caviars

This was my best Woodie. A PS/2 M70 with a 5.25" bay IBM never imagined. When it was on my desk at work it had this 5" floppy drive in it, when I got it home it had a CD drive.

[Linked Image from gfretwell.com]

Greg Fretwell