Corrupt Application or System

A program that keeps crashing or the System crashing, even with extensions turned off is a pretty good sign that the application or System itself has become corrupt.

In the case of a corrupt application, reinstall it from the original disks.

To reinstall the System, launch the Installer, and when you get to the screen that has the Install button, hold down the Command and shift keys and type "K". A dialogue box will appear asking if you want to update the existing System or install a clean System. You want to install a clean System, so click that button and carry on.

The reason for this last step, is that Apple's Installer is smart enough to check items before it replaces them. This is meant to ensure that you don't inadvertently replace more recent version of the System, but it also means that unless you ask it to, the installer won't replace stuff that has become corrupt.

When the installer is finished, you will find a System Folder on your disk, and another folder called Previous System. The Previous System folder contains all of the extensions, fonts and other items from your old corrupt System. Only use these as a last resort. It is ALWAYS a good idea to replace any third party extensions from the original disks rather than dragging them from the old System folder.