Switching Startup Hard Drive

I'm hoping this is the right area to post this question... but:

I have a G5, with 2 hard drives - a 30G (which is the main start up disk) and a 160G.

I've filled up the 30G HD with applications/music/etc. Is there any way to switch the start up capabilities to the 160G HD?

Unfortunately I'm a newly PC to mac convert, so I don't know much anything.

Thanks for any help!!

Sure, but you would need to reinstall OS X on the other harddrive and migrate your user account and settings over.

Just pop in your system disc and hold down the option key to boot from the DVD. Select the second drive as the destination and then during setup select the migration option to move all your stuff over.

Do I need to reformat the 160g HD before I do this?