Mac Extension Conflicts - OS 9
Extensions are files that add functionality to your Macintosh. For example, there is an extension to add network capability and an extension to add printing capability. If your Macintosh did not have these extensions, you wouldn't be able to use the network or print.
Control Panels are similar to extensions in that they add functionality to your Macintosh. They also give you some control over certain settings. For example, there is a control panel for memory where you can set how much of your hard drive is allocated for virtual memory needs.
Extension conflicts or corruption are perhaps the most common cause of Macintosh errors. Some signs of extension conflicts are your computer does not start up properly; repetitive crashing or freezing, or software does not function, as it should. Most extension conflicts manifest themselves in the computer not starting properly. The term "Extension conflicts" includes both extensions and control panels.
One simple way to check if you have an extension conflict is to turn on or restart your computer, and hold down the shift key until you see the Mac logo with the words "Extensions Off" or "Extensions disabled". If the problem disappears when your extensions are turned off, then it is most likely an extension conflict that is causing the problem. If the problem does occur even with extensions off, then it is not an extension conflict - it is either a system problem, or your hardware.
Think back to recall when the problem first started to occur. If you installed any software before or around that time, the extensions that were installed with that software may be the cause of the conflict.
You can check the modification date on your extensions if you can't remember what you installed.
Open your hard drive, then open the "System folder", and then open the "Extensions" folder.
Go to the View menu and select by Name or as List.
If necessary, scroll to the right until you see the "Date Modified" or "Last Modified" column; for newly installed software the "Date Modified" is the date it was installed.
If you find any recently installed extensions, move them out of the Extensions folder and restart your computer. See if you still have the problem. If you do, go on to the next section.Below is the view of the Extensions Manager that appears in Mac OS 9.x.
Using the Extensions Manager, it is possible to determine which extension is causing the problem. For either method 1 or 2 (shown below), go to the "Apple" menu and select Control Panels, then Extensions Manager. The Extensions Manager window will appear. Make a note which extensions are already set to 'off ' (no check mark or "x" to the left) so that you do not turn them on later.
Under "Selected Set", choose "Mac OS base" or "System 9.x base" depending on what system version you have. Restart your computer. If the problem disappears, then one of your non-Apple extensions is causing the problem.Go back to the Extensions manager window. You will now turn on your non-Apple extensions one by one. (Note: do not turn on an extension that was previously off.) To turn on an extension, click on the blank space or in the box to the left of the extension's name. A check mark or x will appear. After turning on one extension, restart the computer and test if the problem still occurs. If it doesn't, turn one more extension on, restart, and test again. Keep repeating this procedure until you find the extension that's causing the problem.
Method 2 - Checking your extensions by halves
Turn off the top half of the list of your extensions, and leave the bottom half on (no matter where they are, leave any extensions that are normally off, off). Restart the computer and test for the problem.
If the problem does not occur, then all the extensions that are on are OK. Leave the bottom extensions as is. Turn on half of the top extensions. Restart the computer.
If the problem occurs at this point, then one of the extensions you just turned on is the culprit. Turn off these extensions one at a time (you'll need to restart your Macintosh each time you turn off an extension) and test for the problem until you find which one is bad.
If the problem doesn't occur, then one of the extensions that are still off is causing the problem. Turn these extensions on one at a time (you will need to restart the Macintosh each time you turn on an extension) and test for the problem until you find which one is a fault.
If the problem does occur then one of the bottom extensions is the culprit. Turn on all of the top extensions and turn off half of the bottom extensions. Restart and test for the problem.
If the problem occurs at this point, one of the extensions you just turned on is the culprit. Turn off these extensions one at a time (restart your Macintosh each time you turn off an extension) and test for the problem until you find which one is at fault.
If the problem does not occur, then one of the extensions that are still off is causing the problem. Turn these extensions on one at a time (you'll need to restart your Macintosh each time you turn on an extension) and test for the problem until you find which one is faulty.If the instructions above are not helpful, Apple has a website page on extension conflict troubleshooting: