Most people do that but it's a bad idea because over time people add applications, have currupt file ect that are not compatible with a new OS.

He's my method for a brand new OS.

Save your existing hard drive to an external bootable
drive using carbon copy cloner. Make sure it boots.
Dismount it. unplug it and everything else connected
to your computer.

Get all your third party Application disc's right next to your computer.
Copy down all your passwords on a piece of paper. Have it there also.
Make a copy of your ISP information.
Get a beverage of your choice. Let's begin.........

Do a clean install which erases your hard drive.
Install Leopard, and configure your isp for internet service.

Begin to install all you MAJOR software first. One by one check to
see if each application works and upgrade each as you go over
the internet.

See where i'm going??? You guessed it. It will take a bit more time
but no where near the time it will take to fix problems created by
currupt and non functional applications.

Have fun....................

__________________
"What you hear in a great jazz band is the sound of democracy. “The jazz band works best when participation is shaped by intelligent communication.”
Harmony happens whenever different parts get to form a whole by means of congruity, concord, symetry, consistency, conformity, correspondence, agreement, accord, unity, consonance…….