how to keep track of users & their usage ?

I have a laptop running windows xp. What is the easiest way of keeping track of users? I want to be able to tell when a user logged in and how long did they use the laptop for. Can you do this through windows or is there a piece of software you can get for this purpose?

if you go to start and run, type eventvwr it will show when it was logged on and off, not great as there's lots of events listed but is a start.