A+: Recording Symptoms and Error Codes

If tests rule out power and interference, proceed to tests focusing on the hardware or software that appears the most likely cause of the problem.

Which test or diagnostic routine is the best one to start with? Before you perform any specific tests, review the clues you gathered from the client. Examples of places where symptoms and error codes can be found include
Event Viewer— The System log records error information regarding drivers and system files, while the Application log records information and errors about applications within the operating system.
Device Manager— If a device in Device Manager is disabled it will be marked with a red x (Windows XP) or a down arrow (Windows Vista); if it is not configured properly there will be an exclamation point against a yellow background (Windows XP and Vista). Device Manager also displays codes in the Properties window of a device indicating particular issues.
On screen messages— Various messages can popup on the screen while a user is working in Windows. Sometimes these messages can be helpful in finding out what the problem is. If the computer fails completely, a stop error (BSOD) will be displayed offering further information as to why the system halted.
The BIOS— The BIOS can indicate errors by way of onscreen messages and beep codes. Use the particular system’s motherboard documentation to discern what these codes and messages mean.
Printer Displays— The small LCD found on many printers (especially laser printers) is used to indicate the status of the printer. From this display you can verify whether the printer is online, if there is a paper jam, identify error codes, and so on.