X61 making strange noises

[onigiri]

I recently purchased an X61, and I noticed that it makes a constant whizzing noise. I suspect it was the fan, did some research and installed this: http://staff-www.uni-marburg.de/~schmitzr/donate.html . On 'Smart' Mode, the noise stopped (the fan is off), but I don't know at what temperature the fan should be on? Manually setting to 3000 rpm, CPU is about ~50C, but setting it to smart mode, the fan is off and the cpu quickly climbs to ~53C. I didn't have a chance to see how far it would go before it turned on, and set it manually back to ~3000rpm.

Some quick questions:
-At what temperature should the cpu be maintained around? What are dangerous levels?
-Is it bad for the fan to be constantly on?

Thanks for your time.

[IvanAndreevich]

You can have the fan stay off until 60-65C easily. I'd say that normal temps on these machines are up to 80C, 85C tops. Anything above that is too hot. 90C is getting into operating, but almost critical territory.