startup disk

Impossible to answer with information provided

Get more information about your computer. Go to the Apple in the upper left corner of any window, then "About This Mac". Copy what it says about "version"and report that here. Now continue to "More Info..." Copy and paste the information here, but omit the serial number and Hardware UUID (if present). Right now the only information with which we have to work is you might be using System 7 dating from the early 1990s since you posted in the Classic software forum.

And even though G4s may not run Mac OS 7, they will at least run some version of Mac OS 9, which is pre-Mac OS X, and is a Classic operating system.

Your nickname suggests you may have a G4. But without further info, it is only guess work.