Step by Step Guide to Fix Windows Stop Code 0x00000040

0x00000040 Error: An Invalid Thread State Transition in Kernel Mode

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What is 0x00000040 Error ?


The Windows Stop Code 0x00000040, labelled TARGET_INVALID, is a Blue Screen of Death (BSOD) that occurs when the operating system detects that a thread has attempted to switch to or access a target that is in an invalid state. This typically signals a critical fault in the management of thread execution, scheduling, or synchronisation during kernel-mode operations. This error may occur sporadically, especially in systems running faulty drivers, unstable kernel-level tools, or misconfigured multi-threaded hardware environments.

Causes

  • Faulty or Misbehaving Drivers: Poorly written or incompatible kernel-mode drivers can alter thread execution inappropriately, leading to illegal state transitions.
  • Invalid Thread or Object Handles: Malfunctioning applications or low-level software might access threads or memory structures that no longer exist.
  • Corrupted Kernel or Synchronisation Primitives: Damaged kernel libraries may mishandle locks, events, or mutexes, triggering race conditions.
  • Overclocked or Misconfigured CPUs: Instability from CPU overclocking may disrupt thread handling and cause invalid instruction executions.
  • Third-Party System Utilities: Debugging tools or system optimisers can interfere with kernel thread management.
  • Incomplete or Failed System Updates: Partially applied Windows updates may break kernel scheduling behaviour.

Resolution Steps




1. Update or Roll Back Device Drivers

  • Press Win + X → Open Device Manager.
  • Focus on system-level drivers (chipset, CPU, graphics) recently updated.
  • Right-click → Select Update Driver or Roll Back Driver if instability began after a driver update.

2. Run System File Checker and DISM

  • Open Command Prompt as Administrator and run:
  • sfc /scannow
  • Then:
  • DISM /Online /Cleanup-Image /RestoreHealth
  •  These commands restore damaged kernel components and synchronisation modules.

3. Uninstall Third-Party Optimisers or Debuggers

  • Go to Control Panel → Programs and Features.
  • Remove system-level optimisers, debuggers, or any tool that modifies thread handling or priority queues.
  • Reboot and check if the BSOD returns.

4. Perform Clean Boot

  • Press Win + R → Type msconfig → Enter
  • Under Services → Check Hide all Microsoft services → Click Disable all
  • Go to Startup tab → Open Task Manager → Disable all items
  • Reboot the system with essential services only

5. Check and Reset Overclocking

If overclocking is enabled:

  • Enter BIOS/UEFI setup (usually via Del or F2 at boot)
  • Restore to Default or Optimised Defaults
  • Save and exit to stabilise CPU thread handling

6. Update BIOS and Chipset Drivers

  • Visit your motherboard/computer manufacturer’s website.
  • Install the latest BIOS version and chipset drivers
  • These updates improve kernel-level thread and interrupt coordination

7. Perform System Restore

If the BSOD appeared after software or update changes:

  • Go to Control Panel → Recovery → Open System Restore
  • Select a restore point before the issue began
  • Complete the on-screen process


The 0x00000040 TARGET_INVALID error reflects a failure in thread execution or transition within the kernel, often caused by driver flaws, synchronisation issues, or CPU instability.

To fix it:

  • Update or roll back drivers,
  • Run system repair tools to restore kernel stability,
  • And remove any software that disrupts thread scheduling.

If none of these steps resolve the issue, consider:

Running advanced diagnostics or resetting overclocked hardware,

Or performing a clean Windows installation to eliminate deep-level kernel faults.

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