Eliminating variables helps determine a problem's cause. You can isolate specific causes by removing unnecessary lines in CONFIG.SYS and AUTOEXEC.BAT. Do not remove lines that are necessary to access the hard disk or to run Windows 95 Setup.
You can also isolate the cause by changing a specific value, and then testing to see if the problem has been corrected or altered. For instance, if you suspect a damaged Registry, you could restore the Registry files (SYSTEM.DAT and USER.DAT) from backup files, and then retest.
If a component fails after upgrading to a new driver, replace it with the original driver and retest. If Windows 95 startup fails while loading a real-mode device driver, or if any device driver is suspect in causing an error condition, you can test the effect of not loading a device driver. To bypass individual, real-mode device drivers, press F8 when the Starting Windows message appears and then select the Step-By-Step Confirmation option. (This process is described in detail in "Safe Mode" later in this chapter.) Removing protected-mode drivers can be done in Device Manager in the System option in Control Panel.
Test each modification individually to see if it solved the problem. Make note of all modifications and their effect on symptoms. This provides you with the information you need to contact product support personnel, if necessary, and provides an excellent reference for future troubleshooting.