Loud fan and diminishing battery

I've had my macbook for about 1.5 years now and today the fan started running really loud and the battery only lasts for about an hour and a half. It's never done this before today. What do you think the problem is?

I had the fan problem. It started after I downloaded a load of ebooks. Turns out that Spotlight was trying to index several gigs of written word. Once I turned Spotlight off, the problem was solved. Of course, that means you have to live without Spotlight.