This may not be related... The only time I ever had a run-away fan is when I tried to install the variant of OSX on a tower that didn't come with it, but rather, was for another model that I was moving to use as a server. I never really dug into why this was so... I'm asuming it was because the drivers needed to work with the sensors to keep the unit cool were not present in the "old" software. Maybe a new install of the original, then an upgrade to Tiger using the drop in DVD? Long shot, but that's all I got! Good luck.