There is a great TroubleShooting guide already installed on Mac.
From Finder, simply press the Help key on the keyboard (or press Command+?):

• Then SEARCH a key word like "freeze" or "conflict."

Also, there's an entire library of support and User Forums at Apple(support).com.

In troubleshooting (OS 9):
If you know what happens when booted with:

• All Extensions Off
• OS 9 Base extensions
• OS 9 All extensions
• My Set (your working set of extensions, and parts thereof)
• Especially: Booting off OS CD,

The rest is ELEMENTARY (once you have done it a few times)....