Stop 0x00000079 or MISMATCHED_HAL

The Stop 0x79 message indicates that the hardware abstraction layer (HAL) and the kernel type for the computer do not match. This error most often occurs when ACPI firmware settings are changed. For example, you might install Windows XP Professional on an x86-based computer with the firmware ACPI enable option enabled and later decide to disable it. This error can also result when mismatched single and multi-processor configuration files are copied to the system.

Interpreting the Message

The content of the information provided by a 0x79 Stop message varies according to the value of the first parameter. Three different values for Parameter 1 are possible. The information in the next two parameters depends upon the value of Parameter 1 as shown in Table C.3.

Table C.3 Parameter Listing for Stop Message 0x79

Parameter 1	Parameter 2	Parameter 3	Description
0x00000001	Release level of Ntoskrnl.exe	Release level of Hal.dll	PRCB release level mismatch
0x00000002	Build type of Ntoskrnl.exe	Build type of Hal.dll	Build type mismatch

When the value of Parameter 1 is set to 0x00000002, the following build type codes become effective:

0x00000000: Multiprocessor-enabled free build
0x00000001: Multiprocessor-enabled checked build
0x00000002: Single-processor free build

Resolving the Problem

The following suggestions are specific to Stop 0x79 errors. For additional troubleshooting suggestions that apply to all Stop errors, see "Stop Message Checklist" later in this appendix.

A Stop 0x79 message occurs when the system is using out-of-date Ntoskrnl.exe or Hal.dll files. This can occur after manual repairs that involve copying incorrect files to the system. This error also occurs when using mismatched files, such as copying a multiprocessor HAL on to a system using a single-processor kernel (or vice versa). The kernel and HAL files for single-processor and multiprocessor systems are stored on the Windows XP Professional operating system CD using two different file names. For example, the single and multi-processor versions of the kernel, named Ntoskrnl.exe and Ntkrnlmp.exe respectively. Setup copies either Ntoskrnl.exe or Ntkrnlmp.exe to your system as Ntoskrnl.exe. In Recovery Console, you can use the Copy command to copy the correct HAL or kernel files from the CD to the appropriate folder on the hard disk. For more information about Recovery Console, see Windows XP Professional Help and Support Center, "Tools for Troubleshooting" and " Troubleshooting Concepts and Strategies" in this book.
If you experience Stop 0x79 messages after changing firmware settings, restore the original settings used during Windows XP Professional Setup.
Because systems that use the ACPI HAL ignore IRQ assignments stored in firmware, you can only manually change IRQ settings for non-ACPI (Standard PC HAL) systems. Some x86-based provide the option to toggle ACPI functionality. To disable or re-enable ACPI, you must change firmware settings and reinstall Windows XP Professional. Because of the numerous registry and system file changes required, you must run Setup again (an upgrade installation does not work).

For more information about Stop 0x79 messages, see the Microsoft Knowledge Base link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources. Search using keywords winnt, 0x00000079, and 0x79.