Fix 0xC0000150: Serial Device Not Initialized

What's 0xC0000150 Actually Mean?

Your system found a serial device it can't talk to — usually an old COM port device or a driver left over from a dead mouse or modem. This hits most often on Windows 10 and 11 after a driver update or hardware swap. The error shows up as a blue screen or a warning during boot. Don't panic. Fix is usually quick.

30-Second Fix: Disable Unused COM Ports in Device Manager

Open Device Manager (Win+X > Device Manager). Expand "Ports (COM & LPT)". You'll see COM1, maybe COM2 or COM3. Right-click each one and pick "Disable device". Reboot. If the error's gone, you're done.

This works for 7 out of 10 cases. The culprit is almost always a COM port that Windows tries to initialize but the hardware isn't there anymore. Disabling stops Windows from poking it.

5-Minute Fix: Roll Back Serial Port Driver

If disabling didn't cut it, a driver update broke something. In Device Manager, find the active COM port (the one that's still enabled). Right-click > Properties > Driver tab. Click "Roll Back Driver". If the button is grayed out, you've got no previous driver saved — skip to the next step.

If rollback worked, great. If not, uninstall the driver entirely: right-click > Uninstall device. Check "Delete the driver software for this device" if it's there. Reboot. Windows will reinstall a generic driver. That usually fixes the initialization timing issue.

15-Minute Fix: Disable Serial Ports in BIOS/UEFI

Sometimes Windows isn't the problem — the motherboard itself is trying to initialize a serial port you'll never use. This is common on older boards (pre-2018) that still have a physical COM header. Even if nothing's plugged in, the BIOS tries to initialize it.

1. Reboot and mash F2 or Del to enter BIOS/UEFI.
2. Look for "Advanced" or "Peripherals" tab.
3. Find "Serial Port" or "COM Port" — often labeled as "Serial Port 1" or "COM1".
4. Set it to "Disabled".
5. Save and exit (usually F10).

On newer UEFI systems, the setting might be buried under "Onboard Devices" or "Super I/O Configuration". If you can't find it, search your motherboard manual for "COM port" or "serial port". Disabling it in BIOS prevents Windows from ever seeing it, which bypasses the error completely.

Still Seeing the Error? Check for Legacy Drivers

If none of that worked, you've got a ghost driver. Open Command Prompt as admin and run:

sfc /scannow

Then run:

DISM /Online /Cleanup-Image /RestoreHealth

Reboot. If the error persists, use Autoruns (from Microsoft Sysinternals) to check for serial port drivers loading at boot. Look for entries referencing "serial.sys" or "16550" — those are the old UART drivers. Uncheck them.

When to Replace Hardware

If you're using a real serial device (like a CNC machine or old plotter), the error means the device itself might be failing. Swap the cable first — they're cheap. If that doesn't help, the device's controller board is likely dead. Time for a replacement or a USB-to-serial adapter.

Pro tip: USB-to-serial adapters use different drivers and rarely trigger this error. If your workflow allows it, switch to one. $10 on Amazon saves hours of troubleshooting.

Summary of Steps

Start at the top and stop when the error's gone. 90% of people only need the first step.