How to fix Error 561 on Windows 11

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Troubleshooting Guide: Error 561 (LDT Resize Failure) on Windows 11

Why This Error Happens

Error 561 is a low-level system error tied to the Local Descriptor Table (LDT), a legacy memory-management structure inherited from the Windows NT/x86 architecture used for segment-based addressing in 16-bit or virtualized application compatibility layers. This error occurs when a process (often an older 16-bit application, a legacy driver, or a virtualization/emulation component) attempts to resize the LDT to a value that is not aligned to an even number of selectors (each selector being 8 bytes), or when it tries to grow the table beyond what the kernel permits at that time. In modern Windows 11 systems, this is almost always triggered by corrupted legacy application binaries, faulty NTVDM/WOW compatibility settings, buggy third-party virtualization software, or corrupted system files handling descriptor tables — it is rarely caused by user-level misconfiguration.

Step-by-Step Resolution Guide

  1. Identify the offending process
    Open Event Viewer (eventvwr.msc) → Windows Logs → System and Application, filter by Event ID 561, and note the source application or service that triggered it. This is critical since Error 561 is almost always application-specific, not OS-wide.

  2. Run System File Checker and DISM to repair corrupted system components
    Open Command Prompt as Administrator and run:

   sfc /scannow
   DISM /Online /Cleanup-Image /RestoreHealth

This repairs corrupted kernel-mode or ntdll-level components that manage descriptor tables.

  1. Check and disable legacy compatibility layers
    If the error stems from an older 16-bit or legacy application, right-click its executable → Properties → Compatibility tab → ensure Run this program in compatibility mode is disabled or set to a supported profile (avoid Windows 95/98/NT emulation modes, which rely on LDT operations no longer natively supported in Windows 11).

  2. Update or remove third-party virtualization/emulation software
    If you’re running virtualization tools (e.g., DOSBox, older VM hypervisors, or legacy emulators), update them to their latest Windows 11–compatible builds via their official sites, since older builds mishandle LDT selector allocation on modern kernels.

  3. Verify Windows Update status
    Go to Settings → Windows Update and ensure all cumulative and driver updates are installed. Microsoft periodically patches kernel-level descriptor handling bugs that can trigger legacy error codes like 561.

Alternative or Verification Steps

  • Verification: Reproduce the original action that caused the error; check Event Viewer again to confirm Event ID 561 no longer appears, and confirm the application runs without crashing or freezing.
  • Alternative: If the issue persists and is tied to a specific legacy 16-bit application, run it inside a dedicated Windows 11 Hyper-V virtual machine with an older Windows OS (e.g., Windows XP/7) installed, isolating the legacy LDT calls from the host system entirely.