Seems perfectly normal to me -- the hard drive has to spin up in order for the OS to load, so that has to be one of the first things that happens during the boot process.
Whether my MacBook's hard drive spins up before or after the chime I can't remember.
If no other things are wrong with your computer, I would say it's perfectly normal. If you suspect something's wrong, though, like it takes an abnormal amount of time to boot, or it feels sluggish, or some other problem, then we may need to investigate farther. As far as I'm concerned though, it's perfectly normal.