You could replace the fan with one that is ball berring and use rubber spacers to limit the noise, as well as using a low RPM drive. Way cheaper than installing a fan w/ a temp gauge.
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MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop