Noisy iMac?

So, when I powered up my fairly new 20" iMac this morning
the system fan cranked up to vacuum cleaner level. It is
loud enough that Bubba the Cat chooses to occupy a different
room, which is not his usual behavior.

This is something that it has not done before. The machine
is in the same location in the same room with an ambient
temperature in the mid 60's(F). It happens immediately
when the system is powered on, so I don't think it is
a reaction to system overheating. The only system software
I've updated lately is Quicktime and BIND, which hardly seem
to be likely causes.

Any ideas?

In article ,
Claude V. Lucas wrote:
>So, when I powered up my fairly new 20" iMac this morning
>the system fan cranked up to vacuum cleaner level. It is
>loud enough that Bubba the Cat chooses to occupy a different
>room, which is not his usual behavior.
>
>This is something that it has not done before. The machine
>is in the same location in the same room with an ambient
>temperature in the mid 60's(F). It happens immediately
>when the system is powered on, so I don't think it is
>a reaction to system overheating. The only system software
>I've updated lately is Quicktime and BIND, which hardly seem
>to be likely causes.
>
>Any ideas?

Never mind.

I found a solution

http://docs.info.apple.com/article.html?artnum=303446

Resettin the System Management Controller shut it up.

For now.

Hopefully this won't be a regular happening.