A few months ago I installed ubuntu on a 1998 imac. The machine turned out to be so useful as a web/google terminal that when I chanced across a 2001 G3/500 for ten bucks on a disposal site I bought it as sort of a spare/additional model with half an idea of using it as a replacement, given that it's twice the speed of the original model, even though it only came with 128MB RAM.
So got it home, turned it on, and found it whined - although it did get better as it settled down, so possibly it's just that the bearings in the fan dried out or something more serious - after all when you pay $10 for something it's no great loss if you end up cannibalizing it for spares.
So, put the ubuntu cd in, held down C as it booted to force it to read the cd. Not a bit of it - it had been configured to boot off the network by default. OK reboot it holding the option key down to get it to scan for a bootable system either on the disk or a cd.
And this is where it got fun. The firmware was password protected, and of course I didb't know the password. However Google was my friend here and came up with a couple of sensible links as to how to reset the password. Now in the instructions it says first add or remove memory from the machine. The machine only had a single 128MB DIMM. At this point I had a senior moment and removed the DIMM. Not surprisingly the machine failed self test as it didn't have any memory in it at all.
So the problem became where to get additional memory. Fortunately it used pc100 DIMMS just like $83 linux machine, so I 'borrowed' some memory from it, brought up the new imac, reset the PRAM, returned the borrowed memory and then rebooted into open firmware, forced a scan, and hey presto we were installing linux.
Well we were trying to install linux, since it was (a) a newer machine and (b) I'm a glutton for punishment I thought I'd try a newer version. Silly boy!. Had as much success as I did when I tried to upgrade the original 1998 imac - ie none. So it's back to the trusty 6.06 distribution. And it works. Runs fine. Possibly I need to buy another one to get more memory, or maybe I should break it up for parts, but at the moment I have 2 ppc imacs running linux. Which is perhaps a little excessive, but Hey, I had some fun and learned some things getting it running ...