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A+ Certification : Operating Systems

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A+ Essentials 220-901  


A+ Practical Application 220-902


3. Diagnosing, and Troubleshooting

3.1 Recognize and interpret the meaning of common error codes and startup messages from the boot sequence, and identify steps to correct the problems.

Common Error Messages and Codes

This error appears if the MBR (Master Boot Record) of your hard drive is not okay. Ensure that that you do not have a floppy disk inserted in your floppy drive. Also make sure that the CMOS setup is pointing to the correct partition in your hard disk. Sometimes, it might happen due to corrupt boot sector. Run any antivirus software to detect and correct boot sector viruses.

The most likely reason is that the, Boot.ini has bad entries. If you are installing Windows NT4, make sure you do not use FAT32. This is because NT4 does not support FAT32.

NTLDR means NT Loader, and the error is associated with Windows NT 4, Windows 2000 and XP.

Solution: Ensure that the file NTLDR is on the root of your boot drive. You have the file in \i386 directory of Windows CD and you can just copy it. You can do this using Recovery Console.

This error comes up if the file is missing or corrupt.  If not, boot with the startup disk (must be the same version or later as the system your trying to boot).and enter the command SYS C:\ at the A:> prompt to copy the system files to the hard drive (Windows 9x only).

This error is usually caused by a syntax error in the CONFIG.SYS file. XX is the line number that the error occurred. Just edit the file using any text editor, and correct the problem.

A line in config.sys to load a himem.sys is missing:

You need to insert the command such as the following in config.sys file: DEVICE=C:\WINDOWS\HIMEM.SYS

9x will load without Himem.sys. If the file is missing, copy it. If the file is corrupt, run scandisk to detect and correct any disk errors.

The error is usually associated with the Operating System failing to start a device or a service. The error may lead to a blue screen, and go no further.  

The device errors are caused due to IRQ/IO conflicts or due to incompatible driver software. Service errors are associated with newly installed software (such as protocols, applications, etc.) or due to missing/corrupt files.

If you have problem booting normally due to failed device/service, boot to the advanced start up modes, say safe mode, safe mode with command prompt etc.

Once in the Safe Mode, you can un-install any recently installed software, run scandisk or any antivirus program. You can also check for any device conflicts, and correct the same (Use appropriate Device Manager).

In very rare cases, you may need to resort to system recovery using installation CD.


The referenced device is no longer installed, or its drivers are missing/corrupted. Try un-installing and then reinstalling the device. Alternatively, remove the referenced lines from the above files.

Event log has finite size, and it may stop recording new events if the log is full. When an event log is full, you will have three options:

1. Clear the existing log, so that new events will get recorded

2. Overwrite the existing log

3. Increase the event log size.

To free an event log, 

  1. Open Event Viewer, click Start, point to Settings, and click Control Panel. Double-click Administrative Tools, and then double-click Event Viewer.

  2. In the console tree, click the log you want to free.

  3. On the Action menu, click Clear all Events.

 To overwrite events,

  1.  On the Action menu, click Properties, and then click Overwrite events. This ensures that all new events are written to the log, even when the log is full.

To increase the log size,

  1.  On the Action menu, click Properties, and then increase the Maximum log size.

Note that you need administrator privileges to effect the above changes.

Explorer.exe could be missing or corrupted

General Protection Errors (GPF): 

Is caused when a program tries to access a portion of memory that  is already being used by another program or TSR. When this happens the screen turns blue with the GPF error message.


  1. Run scandisk/defrag

  2. Remove any TSRs or programs which were running before the GPF.

  3. un-install and re-install the program that caused the GPF.

If you frequently receive GPF errors frequently, try adding more memory. In extreme cases, you may need to re-install the Operating System.

Invalid Page Fault

This is caused when Windows or an application tries to call a block of memory segment that does not exist. This could happen because of bad memory or the application is incompatible or corrupt

Illegal Operation

This is an operation requested, nut not understood by Windows or the CPU. Illegal Operations can be caused by

  1. Corrupt files

  2. Bad Memory

  3. Bad hard drive blocks

  4. Incorrect Drivers

  5. TSRs

Invalid page faults

These are generally caused by program incompatibility, memory faults, etc.

Using the correct Utilities

  • Dr. Watson

  • Boot Disk

  • Event Viewer

Windows 98 drwatson.exe

To start Dr. Watson On the Start menu, click Run, and then type Drwatson. Alternatively, you can use Start|Programs | Accessories | System Tools | and then select System Information | Tools to view Dr Watson.

 Dr. Watson intercepts the software faults, and offers a detailed description of the cause. When enabled, this tool automatically logs this information to the disk (\Windows\Drwatson\*.wlg), and can display it on screen. Values indicated by Dr. Watson include the program that caused the application fault, the program the fault occurred in, and the memory address at which the fault occurred.

Windows 2000 drwtsn32.exe

If a program error occurs, Dr. Watson will start automatically. To start Dr. Watson, click Start, click Run, and then type drwtsn32. To start Dr. Watson from a command prompt, change to the root directory, and then type drwtsn32.

As shown in the figure above, Dr. Watson for Windows 2000 is a program error debugger. A text file is created whenever an error is detected. You also have the option of creating a crash dump file, which is a dump (.dmp) file that a programmer can load into a debugger. Default log file path is C:\Documents and Settings\All Users.WINNT\Documents\DrWatson

        Using Windows 9x, you can create boot disk by any of the following methods:

  1. Using Add/Remove Programs

  2. Using Explorer

  3. Format a:/s

1. Using Add/Remove Programs:

Have a blank Floppy disk ready, and click "Create Disk".

2. Using Explorer: You can also create a boot disk using explorer. Insert blank Floppy disk in the Floppy drive, open Windows Explorer and navigate to A:. Now right click on a, and select Format option. The following Window will open, wherein, you can choose "Copy system files" option to make the disk bootable.

3. Format a:/s This a simpler option without the need for going in for GUI. You just open DOS prompt, and type "Format a:/s" to make Floppy disk bootable soon after formatting it.  You can also run this command from Start | Run.

Using Windows 2000, you can create boot disk using the following method:

  1. Insert a blank, formatted, 3.5-inch, 1.44-MB disk into the floppy disk drive.

  2. Insert the Windows 2000 CD-ROM into the CD-ROM drive.

  3. Click Start, and then click Run.

  4. In the Open box, type d:\bootdisk\makeboot a: (where d: is the drive letter assigned to your CD-ROM drive), and then click OK.

  5. Follow the screen prompts.

    Important: You will need four blank, formatted, 3.5-inch, 1.44-MB floppy disks. Label them Setup Disk One, Setup Disk Two, Setup Disk Three, and Setup Disk Four.


A Event Viewer is a useful tool for viewing error messages. The message logs provided by Even viewer may broadly be classified in to 

  1. Application Logs, 

  2. Security Logs, and 

  3. System Logs.

A screen shot of Even Viewer is given below (for Windows 2000 system).

You can view Event Viewer by going to Control Panel, Administrative Tools, and then selecting Event Viewer. Application log provides any application related messages. System log provides system related messages, and so on. Security log can be programmed to trigger on certain events.

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