Windows BSOD Error 0x00000003 — INVALID_AFFINITY_SET Fix

What Does This Error Mean?

The 0x00000003 blue screen means Windows received an invalid processor affinity setting. This is called INVALID_AFFINITY_SET. It is usually caused by a buggy driver or software that tried to assign a task to a CPU core that does not exist.

Affected Models

Windows 10
Windows 11
Windows 8.1
Windows Server

Common Causes

A driver is sending incorrect CPU affinity values to the Windows kernel
A recently installed program is using outdated or broken threading code
System files are corrupted, causing Windows to misread processor configuration
Overclocking settings have destabilized the CPU or memory
A hardware compatibility issue between your CPU and a third-party driver

How to Fix It

Uninstall any recently installed programs or drivers. Go to Settings > Apps and sort by install date. Remove anything installed just before the crashes started.

Newly installed software is the most common trigger for this error. Start here before doing anything else.
Run the System File Checker. Open Command Prompt as Administrator and type: sfc /scannow

This scans and repairs corrupted Windows system files. It takes about 10 to 20 minutes and may require a restart.
Update all your drivers. Open Device Manager (right-click Start > Device Manager) and check for yellow warning icons. Update any flagged drivers.

Also visit your motherboard or laptop manufacturer's website for the latest chipset and CPU drivers.
If you have overclocking enabled, reset your BIOS/UEFI to default settings. Restart and press Delete or F2 to enter BIOS, then choose 'Load Optimized Defaults.'

Overclocking can cause CPU instability that leads to affinity errors in Windows.
Use System Restore to roll back to a point before the error started. Search 'Create a restore point' in the Start menu and click System Restore.

This undoes recent driver and software changes without affecting your personal files.

When to Call a Professional

If this error appears after every restart and no software fix helps, your CPU or motherboard may have a hardware defect. A technician can run low-level diagnostics to rule out hardware failure. This is especially worth checking if your system is under warranty.

Frequently Asked Questions

What is CPU affinity?

CPU affinity is a setting that tells Windows which processor core should run a specific task. Normally Windows manages this automatically. When a driver or program sends an invalid affinity value, Windows cannot continue and crashes.

Is this error dangerous to my computer?

The crash itself does not damage your hardware. But frequent blue screens can interrupt open files and cause data loss. Fix the root cause as soon as possible to protect your work.

Could my antivirus software cause this error?

Yes. Some antivirus programs hook deeply into Windows at the driver level. If the antivirus driver has a bug, it can trigger rare errors like this one. Try temporarily disabling your antivirus to see if the crashes stop.