Here are a couple of links you can look at. The first one is on some modifications that a user made himself, and the second one is for a company in germany called verax that developed two fan kits for the MDD G4.
I bought and installed the two verax kits in my MDD G4, which was rather pricey at $300.00 (US).
The first kit replaces the two small fans that cool the power supply. The second kit replaces both the main fan, and a heat sink with two small fans on top of it as well.
The results? Well when I first rebooted after installation, I couldn't believe the difference that it made (I could hear the hard drive, instead of the vacuum cleaner fans). It was very quiet, especially compared to the original fans and even the kit that Apple offered with the replacement program.
I personally noticed what I would call an area of concern with the verax kit in my installation.
I have always run a program called temperature monitor that monitors the temp of your processors, and with either Apple fan I was always in the mid 50's celsius. With the verax kit the temp jumped up into the mid to high 60's celsius.
Now I am not blaming this all on the kit, as where my setup is at currently has very poor air flow, at least compared to where it was at before. This in itself, did lead to increase in temps, both with the Apple fans and the verax kit.
I did contact verax with my concerns, as I was worried about frying one of my processors. They were very quick to reply, saying that the temperature ranges that my machine was in was well within the specs for these processors, and that there should be no concern. They also added, that the machine is setup to shutdown by itself, should the temps ever get to high to prevent damage.
That did help ease my concerns a little, but still not satisfied, I decided to add a pci slot fan to my machine. I bought one from CompUSA, and installed it. The results were temps that stay around 61 C, but did increase the noise level slightly, although nowhere near what it used to be.
Just thought I'd let you know, as the verax kits are a lot of money. They are nice and easy to install, and your results may vary especially if your setup is in a better ventilated area.
http://www.xlr8yourmac.com/systems/...s/noise_reduction/g4_ddr_noise_reduction.html
http://www.veraxfans.com/
