*ssaloon
-what freeware are you using to check the rpm of your fans?

*frenchtower
-i'm using 10.5.8 (it's the latest upgrade i suppose). my unit is 3yo and it started producing this sound about a year ago. it's actually sporadic. times are the noise gets really loud (when watching youtube) and often times it gets low, but still can hear it.
you see i just think this is one of apple's perennial problem with their notebooks as there are thousands out there whining over this similar situation. good thing yours is fine.
-i'm on the verge of wanting to open the unit, as warranty isn't applicable anymore being 3yo. just that it's alittle scary as this will be the first attempt to do this and i don't want to spoil the unit and end up feeling sorry.

Thanks guys for the responses. will try to search more and see the best option.