PRB: KRNL386: Unable to Enter Protected Mode

 Last reviewed: July 23, 1997
Article ID: Q105207
3.10 WINDOWS kbsetup kbprb

The information in this article applies to:

  • Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SYMPTOMS

Windows 3.1 fails to boot and returns to MS-DOS with a "KRNL386: Unable to enter Protected Mode" error message. This usually occurs after switching to the debug version of Windows.

CAUSE

Windows 3.1 was started with old files left over from an upgraded installation of Windows 3.0 with the Windows 3.0 Software Development Kit (SDK).

RESOLUTION

Replace the old files with the correct versions. The files of importance are KRNL386.*, KRNL286.*, GDI.*, and USER.*. The old files are from 1990 and the new files are from 1992. Sort by date, and replace these old files with the correct versions.

MORE INFORMATION

It's generally a good idea to start with a fresh installation of Windows in a clean directory when this problem occurs. This ensures that other obsolete files are cleared from the upgraded 3.0 installation.

Additional reference words: 3.10
KBCategory: kbsetup kbprb
KBSubcategory: KrDebug
Keywords : kb16bitonly

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Last reviewed: July 23, 1997
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