This will eliminate the flashing question mark at startup, which is caused by the computer resetting it's default startup disk to a nonexistent network server in OS 8.5 or later. Of course, if you are a client computer running off a network server, leave it on the network disk. Dealing with Extension and Control Panel problems. Probably the single largest cause of operating system freezes and crashes are extension conflicts, and, to a lesser extent, control panel conflicts. When two or more of them try to load, or grab control of the computer at the same time, you have a conflict.
Control panels can do the same thing.
The Extensions Manager control panel allows you to deal with these problems by disabling, or turning off, individual extensions, and by creating specific sets of extensions that include or exclude particular extensions or control panels that are in conflict with each other. For example, if your Iomega Zip driver extension is causing conflicts with several other extensions loaded by other application programs, you can create an extension set that includes all extensions except the Iomega driver, and use that as your standard set except when you need to use the Zip drive. You can also create a set that includes the Iomega driver, and excludes those particular extensions that it conflicts with, which you would use when using the Zip drive. You then select the desired set from the extensions manager, and restart to load only the desired set of extension and control panels. If this resolves your freezes or crashes, you know that one of the third party extensions or control panels is causing your problems.