How to Fix System Thread Exception Not Handled

System Thread Exception Not Handled is a Windows blue screen (stop code 0x0000007E) that appears when a driver runs into an error Windows does not know how to handle, so it stops to stay safe. It is almost always caused by a faulty, outdated, or incompatible driver, and the screen sometimes names the file responsible, such as a graphics driver. You fix it by updating, rolling back, or replacing that driver.

Why this happens

A driver runs deep inside Windows. When one throws an error that is not caught, Windows cannot continue safely and triggers this stop error. The failing file name shown on screen is your best clue.

• An outdated or corrupt driver, most often the display or graphics driver.
• An incompatible driver left over after upgrading Windows.
• Corrupt Windows system files.
• A recent driver or Windows update that introduced the fault.
• Occasionally faulty RAM or an overheating component.

Is this normal?

No. It points to a specific driver or file fault. If it happens once it may be a glitch, but if it repeats or loops there is a driver that needs attention.

Does it cause any problems?

Yes. It crashes the PC and can loop on startup, keeping you out of Windows. Until the driver is fixed, the machine may be unusable, though your files remain safe on the drive.

How to fix or check it

1. Read the file name in parentheses on the blue screen if one is shown, such as nvlddmkm.sys or a similar driver file, and note it.
2. If Windows will not boot, force it into the Recovery Environment and choose Startup Settings, then boot into Safe Mode.
3. In Safe Mode, open Device Manager, find the device for the named driver, and use Roll Back Driver, or uninstall it and reinstall a fresh copy from the maker's website.
4. If no file was named, update your graphics, network, and chipset drivers from the manufacturer sites.
5. Open Command Prompt as administrator and run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth to repair system files.
6. Run the Windows Memory Diagnostic (mdsched.exe) if crashes continue, to rule out bad RAM.
7. If it started after a Windows update, uninstall that update or use System Restore to return to a working state.

Frequently asked questions

How do I know which driver caused it?

The blue screen often shows a file name in parentheses ending in .sys. Search that name to identify the device, then update or roll back that specific driver.

Why does it keep looping on startup?

If the faulty driver loads early, Windows crashes before it finishes booting, so it loops. Safe Mode loads a minimal set of drivers, letting you get in and fix the problem one.

Can bad RAM cause this error?

Yes, though it is less common than a driver fault. If updating drivers and repairing files does not help, run the Windows Memory Diagnostic to check your RAM.