My iBook is (or will be, rather) a 900mhz 14" G3 (dual usb). The two questions that I've got are:
1: How big of a Hard Drive can it handle? I know that it can physically take a WD 250gb IDE, but have heard that it can only acknowledge 80gb, or 120gb, or 160gb... Everyone seems to have a different figure. Does anyone know what this thing can take?
2: What can I do to keep it a bit cooler, aside from the stands? I've heard rumblings of more powerful fans, but what would I even look for in that area? Would making some small vent holes around the hard drive help dissipate some of the heat?
Thanks for your time-

According to Apple, it will handle drives "larger than 128gb". I don't know for sure if it will go all the way up to 250, but it would make sense that the next logical step would be 256gb. Here's the article. http://support.apple.com/kb/HT2544?viewlocale=en_US

You shouldn't have an issue with drive size since your machine should have the updated ATA interface which supports larger drives.

If there actually were an issue, you just have to partition the drive. You'd be able to use the 250gb drive anyway.

Good good.
So how can I keep this thing ventilated better? I'm thinking of drilling a pattern of small holes above the hard drive in the palm rest to try to let some of the heat out... Maybe make a little copper heatsink/pipe running out the side?

First step:
De-dusting. Take off the shielding and blow it clean with some compressed air.

Next:
G4FanControl, lower your fan's speed/temperature threshold. It will keep it running nice and cool. (albeit a little louder, but compromises
compromises...)

The holes above the hard drive wouldn't do very much, as the HD usually doesn't come above 35C, even during heavy use. If your 250GB drive is a 7200RPM, you should do a test run with high disk activity to see what temperature it averages.

As far as heat-pipes go, the GPU would be a good target. It's the hottest running component in that system. Added to the fact that there's ample space within a 14 incher for some improvement on the cooling.

The hard drive I'm considering is a 5400rpm. I haven't had the computer together for a year or two, but I do remember how warm it would get; I guess I'd just like to cool the hell out of it as long as it's apart.
To be perfectly honest, I'm more accustomed to engines and machining parts than the inner workings of these little beasts!

They're fun little buggars.

Another measure would be to polish the heatsink and replace the thermal pads. The existing ones are probably toast by now.