Fix:
Create C:\Windows\System32\DriverStore\FileRepository\serial.inf_amd64\serial.inf modification to mark driver as always installed.
| Windows 10 Version | PNP0500 Status | Workaround |
|--------------------|----------------|-------------|
| 1507 (RTM) | Working | None needed |
| 1607 (Anniversary) | Broken for some ACPI tables | Add legacy hardware |
| 1809 | Working | Use COM port number > COM8 |
| 20H2/21H1 | Works but requires driver signature override | Boot with bcdedit /set testsigning on |
| 22H2 (latest) | Works only if serial.sys is present | SFC /scannow | pnp0500 windows 10 portable
If you run Windows 10 from a USB drive and need serial ports on multiple PCs:
If the error appears during installation to a portable drive (not while booting an existing portable OS), the problem is likely partition-related. Once cleaned and converted, restart the Windows installation
Steps to fix partition style:
Once cleaned and converted, restart the Windows installation. The PNP0500 error should vanish. Some portable devices (e
Cause: Missing or corrupted serial.sys in portable Windows
Fix: Copy from C:\Windows\System32\drivers\serial.sys from a working Windows 10 installation. Place in same location on portable drive. Then:
reg add "HKLM\SYSTEM\CurrentControlSet\Services\Serial" /v Start /t REG_DWORD /d 1 /f
Some portable devices (e.g., rugged tablets, embedded systems) need an older serial driver:
| Feature | PNP0500 | PNP0501 | |---------|---------|----------| | Hardware | Native motherboard COM port | USB-to-UART bridge (Prolific/FTDI/Silabs) | | Driver | serial.sys | ser2pl64.sys, ftdibus.sys, etc. | | Portable issue | IRQ conflicts | Driver signing / driver reset | | Best fix | Reserve COM port via BIOS | Use Zadig to replace driver |
On portable Windows, prefer USB-to-serial adapters because they are hardware-independent. Legacy PNP0500 ports on laptops/desktops may not work if the motherboard chipset driver isn't installed.