How to fix Error 155 on Windows 11

by

Why This Error Happens

Error 155 (“Cannot create another thread”) occurs when the Windows Kernel is unable to allocate the necessary resources for a new thread, typically due to exhaustion of the non-paged memory pool or the process/system hitting its maximum handle and thread limits. This is most commonly caused by a “resource leak” — a poorly coded application, an outdated driver, or a background process that continuously spawns threads/handles without releasing them. In some cases, an undersized Windows page file (virtual memory) prevents the OS from allocating stack space for new threads, especially under heavy multitasking loads.

Step-by-Step Resolution Guide

  1. Identify the Resource Hog via Task Manager
  • Press Ctrl + Shift + Esc to open Task Manager.
  • Go to the Details tab, right-click the column header, and select Select Columns. Enable Threads and Handles.
  • Sort by these columns to identify any single process with abnormally high counts (e.g., thousands of threads/handles). End that task if it’s a non-critical app.
  1. Increase the Virtual Memory (Page File) Allocation
  • Press Win + R, type sysdm.cpl, and hit Enter.
  • Go to Advanced > Performance Settings > Advanced tab > Change (under Virtual Memory).
  • Uncheck Automatically manage paging file size for all drives.
  • Select your system drive (usually C:), choose Custom Size, and set an Initial size of 1.5x your RAM (in MB) and Maximum size of 3x your RAM.
  • Click Set, then OK, and restart your PC.
  1. Update or Roll Back Faulty Drivers
  • Open Device Manager (Win + X > Device Manager).
  • Check for devices with a yellow warning icon, particularly under Network Adapters, Display Adapters, or Storage Controllers.
  • Right-click the flagged device, select Update Driver, or if the issue started after a recent update, choose Properties > Driver tab > Roll Back Driver.
  1. Run System File and Disk Checks
  • Open Command Prompt as Administrator (Win + X > Terminal (Admin)).
  • Run the following commands sequentially to repair corrupted system files that may be mismanaging thread pools:

    sfc /scannow
    DISM /Online /Cleanup-Image /RestoreHealth
  • Restart the PC once completed.
  1. Perform a Clean Boot to Isolate Third-Party Conflicts
  • Type msconfig in the Run dialog and press Enter.
  • Under the Services tab, check Hide all Microsoft services, then click Disable all.
  • Go to the Startup tab, open Task Manager, and disable all non-essential startup items.
  • Restart the PC and monitor if the error persists.

Alternative or Verification Steps

  • Verify the Fix: Reopen the application that previously threw Error 155 and monitor the Threads count for that specific process in Task Manager over 10–15 minutes; a stable or slowly increasing count confirms the leak is resolved.
  • Alternative Fix: If the error persists, check for a corrupted user profile by creating a new local Windows user account (Settings > Accounts > Other users > Add account) and testing if the error occurs under the new profile.