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Microsoft KB Archive/101096

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Knowledge Base

Error Message: STOP: C0000221 Unknown Hard Error or STOP: C0000221 STATUS_IMAGE_CHECKSUM_MISMATCH

Article ID: 101096

Article Last Modified on 2/20/2007


  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows NT Advanced Server 3.1
  • Microsoft Windows NT Server 3.5
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
  • Microsoft Windows NT Workstation 3.1
  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Advanced Server 3.1

This article was previously published under Q101096


The following STOP message appears when a critical system file or other file needed to load Windows is corrupted:

STOP: C0000221 unknown hard error
<path>\<file name>

Alternatively, the error may read as follows:

STOP: 0xC0000221 unknown hard error
c:\winnt\system32\ntdll.dll (or other specific file/driver)

In Windows 2000 the error reads as follows:

<path>\<file name>

This error can appear in many different formats, ranging from a blue system error screen to a dialog box. The type of format depends on how much of the operating system was loaded when the corrupted file was detected.


If you receive this error message, the file listed in the error message is corrupted.


To resolve this issue, you need to either obtain a new copy of the file or reinstall Windows. If reinstallation fails to solve the problem, a hardware or network problem may exist.


The files that are checked for integrity when Windows starts are:

  • All drivers (except those loaded by the system loader to boot the system)
  • All dynamic link libraries (DLLs), including USER, GDI, SHELL, KERNEL, NTDLL, CRTDLL, etc.
  • All DLLs loaded into the address space of the Windows server (video drivers, printer drivers, etc.)

This error message can be caused when you install an inappropriate driver for your hardware. For example, this error would appear if you installed a MIPS driver on an X86-based computer.

Additional query words: prodnt checksum blue trap

Keywords: kbother kbprb KB101096