what does windows xp do while booting up?

My problem is, that it takes a long time until my OS [XP] has booted
up.
I disabled all unnecessary programs, drivers and services but it
didn't improved the situation very well. So I defragmented my
harddrive and it got a bit better. I think there must be one or two
drivers or programs, which cause this problem.
Is there any way to see which processes windows loads at the start up
and how long it takes time?
.