Your Powerbook User's Guide has instructions for doing that. If you don't have it anymore, try Apple's Website.
Hi thanks for the info,after all that my son remembered what the password was lol,i tried useing the os x install disc to reset password but for some reason it would not allow me too,thats why i wanted to find out if and how i could format and start again,,,bloody kids :)
I am not sure if you were using OS X or OS 9 with your powerbook.
Anyways, either an OS 9 or an OS X install disk will give you the option to format the hard drive. You may need to look into the customize button before making the install, and there are options there to format the hard drive, or keep data in it's place.
Older computers could be booted with a Floppy disk and format the hard drive that way, and some of the older powerbooks had what was called SCSI Disk Mode that you could attach it to another system, and format the drive that way.
Easiest to do is to boot with an install disk, and find the format option.