Windows includes a built-in architecture driver ( serial.sys ) specifically designed to run this hardware automatically without requiring third-party software. Common Reasons to Update the PNP0500 Driver
System administrators are advised to push this update to relevant workstations to ensure continuity of serial communications.
Here are a few options for a post about a "pnp0500 driver updated" event, depending on where you are posting (e.g., a tech blog, a company update, or a forum). pnp0500 driver updated
If the rollback option is greyed out, you must manually point Windows to its stable, built-in legacy driver asset.
| Issue | Likely Cause | Solution | | :--- | :--- | :--- | | in Device Manager | Corrupted driver, resource conflict (IRQ/I/O address), or disabled COM port in BIOS. | Re‑install driver (Method 3 above). Check BIOS settings to ensure the serial port is enabled and not conflicting with another device. | | “PNP_DETECTED_FATAL_ERROR” blue screen | Problem with a Plug and Play device or its driver, often a recently added peripheral. | Disconnect all non‑essential USB devices, then update all drivers via Windows Update. | | Serial device not communicating | Incorrect baud rate, parity, or other settings in the application; or driver not loaded. | Check the communication parameters (speed, data bits, stop bits). Use a terminal program like PuTTY to test the port. | | Driver fails to install/update | Windows file corruption or pending updates. | Run System File Checker : sfc /scannow from an elevated Command Prompt. Then restart and try again. | | COM port missing after Windows upgrade | The legacy port was disabled by the upgrade or a new driver is required. | Check BIOS for serial port settings. If enabled but still missing, use “Add legacy hardware” in Device Manager to manually add a standard COM port. | Windows includes a built-in architecture driver ( serial
Some users have reported random freezes or boot failures on older systems (e.g., ASRock Z77) where driver conflicts or hardware failure (like SSD or PSU) mimic driver issues.
If your PNP0500 driver is updated but the port still refuses to work, try these diagnostic steps: Check BIOS/UEFI Settings If the rollback option is greyed out, you
Legacy serial ports can be completely disabled at the hardware level in your system BIOS.
The PNP0500 ID is a universal industry standard [2, 3]. Whether you are using an older Intel D945GNT motherboard or a classic Lenovo ThinkPad T61 , this driver identifies the hardware correctly so the OS can communicate with it [5, 6].
: Use the official Microsoft "Show or hide updates" troubleshooting tool ( wushowhid.diagcab ) to scan for pending updates and explicitly hide the PNP0500 driver payload. Step 4: Adjust BIOS/UEFI Settings
You might also see a PNP0501 device in your Device Manager. PNP0501 is essentially a sibling to PNP0500 and is also used for 16550A-compatible COM ports. The same driver or a very similar one works for both, so the update procedure is identical.