Hi, gsrcivic619 -
In order to do a Clean Install on the startup drive, with or withut erasing the drive, you will need to boot the machine to the Install CD. To do that, with the CD in the drive restart, then immediately press the C key, keep it held down until the machine has started to boot to the OS on the CD. This will take longer than booting to the hard drive, so wait it out.
Article #TA43881 - Mac OS 8, Mac OS 9: Performing a Clean Installation
If you do want to erase the hard drive, you can do so while booted to the Install CD. Be sure you have first backed up any data you do not want to lose. To erase and reformat the drive, you will use the Drive Setup utility which can be found in the Utilities folder on the Install CD.
Using Drive Setup
Be sure to select Mac OS Extended as the format when asked.
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Under these circumstances many folk prefer to do a deep wipe of the drive rather a simple erase.
A simple erase just trashes the existing disk directory (the map that tells the OS what files are locate where on the drive), but leaves the data itself intact; over time the old data will get overwritten by new files.
A deep wipe will ensure that the old data is no longer present. To do this, whien you first start up Drive Setup and select the dribe in the list, go to the Funtions menu and select Initialization Options; in that window choose Zero All Data or Low Lwvel, whichever is offered; then click the Initialize button. Note - Zero All Data can take a while, about one hour per each 10GB of drive size.