When you start your Macintosh, the system software loads extensions in alphabetical order, first loading system extension files in the Extensions folder, then control panel files in the Control Panels folder, and finally both system extension and control panel files in the System Folder. All extensions are enabled once the system loads them, except for control panels you've disabled. An extension can be the cause of a system problem, such as a system error, when it conflicts with an application or another extension, or when it is incompatible with your operating systemor is corrupt.
Problems can also arise due to incompatibilities with a particular setting in a control panel.
Disabling Extensions To determine if one or more extensions are the cause of a problem, you must first disable all added extensions. You can then try to re-create the problem. Restart your Macintosh with the Shift key held down. Use an extensions manager. Keep in mind, however, that any extension you use to disable other extensions may itself be contributing to the problem.