My son told me he may have accidentally trashed the system folder. Upon startup there is no chime, there is the Apple icon then a screen of what looks like programmers code over a message box which says to shutdown and restart. Of course, this does not work.
I have tried restarting holding down option which gets me to a screen with a refresh button and a right arrow button. There is also an icon identifying his computer. The refresh button does nothing and the right arrow button just takes me back to the screen mentioned above.
I do not have the original system install disk but tried an iMac install disk with no results.
What can I do to fix this?

That would be a kernel panic and due to the trashing of the system folder, you'll need to reinstall the OS. The iMac restore cd won't work. You'll need the restore cd for your machine or a generic OS X install from a retail store.

Thanks Justin,
We installed OS X 10.3 and the computer is up and running again, although it is somewhat slower than it was before. We are working on it but we're glad the main problem has been fixed.