Fan comes on when viewing web video or flash
When viewing video online, say YouTube or playing Mafia Wars on Facebook, the fan will come on and rev up very high. Stop and the fan will eventually turn off.
This isn't a recent thing, has been happening forever. Replaced the battery not so long ago and that didn't make a difference. The only mod make to this laptop was upgrading the wireless card to a N card.
2ghz Intel Core Duo