My usual setup is a MBP with an external Cinema Display. I leave the lid on the notebook closed, and just use the Cinema Display. I also have an external HD plugged in via Firewire 800, and an Apogee Duet for audio. Recently I've become plagued by very fast fan speeds a lot of the time. When the fan is up around 5000 - 6000 rpm, it makes a lot of noise. I've tried all the usual stuff for resetting the OS, using SMCFanControl, etc. I'm not talking about excessive CPU usage - CPU is around 75% idle. I'm wondering what effect using the external display has, and what effect it has with the lid closed on the MBP. I've been trying it out in different combinations, and so far it seems that the external display adds quite a bit to the fan speed. It doesn't seem to relate directly to the temperature though. Maybe it is just set to run the fan about 1000 rpm faster when the external display is plugged in - perhaps due to extra load on the video card. I'd be interested to hear from other people who use a Cinema Display with their MBP, whether they have fan speed issues. I guess opening up the notebook lid might help with cooling, although it doesn't really suit me.