overvolt stock P4 fan?

Is it possible to overvolt the fan on the stock P4 HSF? For the purpose of getting more RPMs out of it of course. Mine generally spins between 3200 and 3400 RPMs. Would this be safe to do? Any suggestions or links would be great

it sure is. but the fan might not last too long.
then again it might last forever.

http://www.overclockers.com/tips808/