NTOSKRNL.EXE is Missing or Corrupt

What is the NTOSKRNL.EXE anyway? Well, it is a Windows system file that is located in the Windows\System32 folder on your system disk. It is basically a kernel image of the operating system, and it is critical in Windows operating systems. The file is loaded at computer startup, so the error message “NTOSKRNL.EXE is missing” will appear during the start up phase in case of an error. Related files and error messages can indicate problems with the “hall.dll”, or “ntdll.dll” Windows library files.

What Causes NTOSKRNL.EXE Errors?

NTOSKRNL.EXE errors are mostly caused by a missing or corrupt ntoskrnl.exe or hall.dll file, or by a missing or corrupt boot.ini file. All these files are required during Windows startup, so any problem with the files will cause Windows not to start.

The first requirement is to start your system, which will require a bootable XP CD-ROM or DVD. In the case of W2K, you need the Emergency Repair Disk. Boot NT from the setup disks and select R in the boot menu, after which you will need to enter the ERD. For XP, start from the CD-ROM or DVD and in the setup menu, select R for recovery. Next you will need to select the installation you want to repair and enter the admin password.

To restore the ntoskrnl.exe and/or hall.dll files type these commands at the prompt (each followed by pressing the Enter key):

expand d:\i386\ntoskrnl.ex_ c:\windows\system32
expand d:\i386\hal.dl_ c\windows\system32

Note: This assumes that the Windows system disk is drive C: and that the CD/DVD drive is drive D:. Please modify the command in case your drive letter assignment is different.
When prompted, type a Y and press Enter to overwrite the files during the expand command. Once the files are restored, remove the CD-ROM or DVD and reboot your PC.

BOOT.INI Problems

If the previous action did not solve the problem, the boot.ini file can be the cause of the ntoskrnl.exe error. The boot.ini file is a relatively small text file that stores the configuration of the operating systems on your PC. The boot.ini file is always located in the root of the boot disk, so mostly in C:\.

An example of a boot.ini file looks like this:

[boot loader] timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS=”Microsoft Windows XP Professional” /fastdetect

The timeout value indicates how long the boot menu is shown in case of a multi boot configuration and the [operating systems] section contains entries for each configuration, basically where the operating system is located and using what name it is listed in the boot menu. More details can be found on the Microsoft support site.

If you want to see the boot.ini file, you can access the contents from the System option in the Control Panel (Advanced tab, Settings button in Startup and Recovery), or you can open the system root (C:\) in the Windows Explorer. You will need to enable displaying system files and unhide hidden files before you can see the boot.ini file.

Rebuild the BOOT.INI File

Although you can manually edit the boot.ini file to solve Windows startup errors, the easiest way to restore the boot.ini file is to rebuild it. For this you would again need to start your PC from the Windows XP CD-ROM or DVD. In the setup menu, press the R for the recovery console, select the installation to repair and enter the admin password.

This time, when you see the command prompt, type the command below followed by Enter:

bootcfg /rebuild

The program will search your hard disk(s) for Windows installations (NT, 2000, XP) and show you the results. For each installation it finds, you need to select if you want to add the installation to the boot list (Y) or not (N). When prompted to “Enter Load Identifier”, type the name with which you want to see the installation in the boot menu (this is really only important when you have a multiple boot configuration), and press Enter. When prompted to “Enter OS Load Options”, type “/fastdetect”, which instructs the installation to automatically detect options.

When no new installations are found, you need to type “exit” and press Enter to exit the recovery console and restart your PC.

Further Steps…

Of course there is a reason for any of the Windows system boot files to get corrupted, so once your system starts again, run a chkdsk (check disk) to verify the integrity of your hard disk. It could be that the ntoskrnl.exe error was caused by turning off the computer while it was still shutting down, but in the worst case scenario, your disk has real problems that need to be fixed.