How to fix CLASSPNP.SYS error in Windows 10/8/7 for good

Tashreef Shareef
by Tashreef Shareef
Windows & Software Expert
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fix_CLASSPNP_SYS error

Classpnp.sys is a Microsoft Windows SCSI class system file that comes as part of the Windows OS. While the regular users never need to know about the CLASSPNP.SYS file, at times you may encounter errors related to such critical system device drivers.

The CLASSPNP.SYS error is a BSOD error, and it leaves the affected PC unusable. The error can occur due to several reasons including hardware failure and software corruption.

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Most of the cases of CLASSPNP.SYS error is related to hardware failure, whereas some users have reported the error to have appeared after installing a game and other Windows applications.

In this article, we walk you through all the possible solutions to fix CLASSPNP.SYS BSOD error in Windows 10, 7 and 8.

Steps to fix CLASSPNP.SYS BSOD errors

Solution 1: Uninstall recently installed programs

Some of the Windows users have reported the CLASSPNP.SYS error to have appeared after installing a video game or software. In such a situation, it is highly likely that the software is causing the error.

Uninstall Program Windows 10

Representational image – the program is not related to the error.

If you are able to boot into Windows and go past the login screen, try to uninstall the game or software. Now, restart the PC and check if the issue is resolved.

Solution 2:  Disconnect External Hardware/ Peripherals

Another common cause of CLASSPNP.SYS error is peripheral devices. If you have connected hardware like a USB mouse, external hard drive, Bluetooth dongle for a wireless mouse, external cooler and any other device to your laptop or PC, try disconnecting them.

Shutdown your PC. Disconnect one of the peripherals and restart the PC. Do this until you have fixed the problem, or all the external devices are disconnected.

If the error is due to an external device, you can keep it unplugged for a while and check if it works with other devices. This should allow you to inspect the hardware for any fault.

Solution 3: Boot Last Known Good Configuration

Windows OS stores a copy of the system’s hardware configuration and driver settings taken from the system’s registry. In case of boot process failures, the OS adds the Last Known Good Configuration option to the startup menu.

If your PC has already detected multiple boot failures, you can use the Last Good Known Configuration option to boot normally.

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Windows OS will automatically display the Boot Last Known Good Configuration option after multiple failed attempts to boot the OS.

Or You can manually access this option by pressing the F8 key until the Startup option screen is displayed. Make sure you start pressing F8 key before the Windows starts to boot.

Note: In Windows 8 and Windows 10, the Last Known Good Configuration option is disabled by default. You need to enable it manually from the Registry Editor.

Solution 4: Change SATA Mode Setting in BIOS

Your PC is configured to use IDE or ACHI mechanism to configure with SATA (Serial ATA). A good number of users have reported that changing the SATA mode in BIOS settings has helped them fix the CLASSPNP.SYS error.

To enter BIOS settings, restart your PC and start pressing F2 until you see the BIOS screen. The shortcut key may differ depending on your laptop maker.

In the BIOS setting change the disk mode from AHCI to IDE temporarily. Save the changes and exit the BIOS screen.

Note: If the SATA mode is already set to IDE, try changing it to the next available setting that is AHCI or Compatibility mode.

Restart your computer and check if the CLASSPNP.SYS error is resolved.

Solution 5: Remove Internal Hardware

The CLASSPNP.SYS error can also occur due to internal hardware failure. If you have a faulty RAM or hard drive, it can prevent Windows from booting normally.

If you have added RAM stick, video card or PCI-e card, try removing them temporarily.

Even if you haven’t added any new hardware, try to remove extra RAM, video-card or PCI-e card or wireless card and restart the computer. You can reinsert the hardware if the computer boots normally.

If you only have a single unit of RAM but an empty slot alongside, remove and insert the RAM into the empty slot.

Alternatively, you can also use Memtest86+, a memory module checking software and create a bootable USB drive from it to check for the bad memory module. You can download the Memtest86+ ISO from the official website.

Make sure you create a bootable flash drive or CD first. Boot from the USB drive and run a memory test to check for the bad memory module. When detected, remove the bad memory modules and reboot your PC.

Solution 6:  Run System File Checker

Microsoft Windows OS comes with a built-in System File Checker utility. It allows the users to check for corrupt or missing system files and fixes them by replacing the missing file with the cached version of the same file.

If you are able to boot into Windows, open Command Prompt as administrator and type the following command: sfc /scannow

If you are unable to boot into Windows, here is how to run System File Checker from Recovery mode.

You can enter Recovery Mode from the login screen, Advanced Repair Option or Recovery screen. Assuming that you are unable to boot into Windows, you are left with two options. Here is how to do it.

Option 1: When your PC fails to start multiple times, Windows 10 presents you with a Recovery screen. From the Recovery screen, click on See Advanced Repair Options.

Option 2: Alternatively, you can also get into Recovery Mode by pressing the F8 key.

Shutdown your PC. Press the start button and start pressing F8 until you see the Recovery screen.

Run System File Checker from Recovery Mode

  1. From the Choose an option screen, click on Troubleshoot option.
    Windows 10 Recovery Option_1
  2. Click on Advanced Options. Under Advanced Option, select Command Prompt.
    Windows 10 Advanced Option_1
  3. Upon restart, enter the following command in the command prompt window.
sfc /Scannow

If that command didn’t work, try this. This command will only check for error in C:drive

 Sfc /scannow /OFFBOOTDIR=C: /OFFWINDIR=C:Windows

The System File Checker will now scan the C: driver for corrupt or missing files and try to repair it with new files.

Solution 7:  Restore Windows to Earlier Point

All the Windows PCs come with System Restore option. The System Restore features allows you to create a System Restore Point and save it in your local drive.

Windows automatically creates a Restore Points and saves a working copy of your system before making any major changes like applying new updates or installing an app.

If anything goes wrong with your system, you can revert back to the working state by restoring the PC to an earlier point and undo system changes.

You can access the System Restore properties either from the desktop or Recovery option.

Option 1: If you can log in and access the desktop, do the following.

Type Restore in the Cortana/Search bar and select Create a System Restore Point option. This will open the System Properties window.

Option 2 : If you are unable to log in or boot into Windows, do the following:

  1. When the PC fails to start the boot process multiple times, it will show a Recovery screen (Automatic Repair screen). From the Recovery screen, click on See Advanced Options.
  2. The PC will restart with Choose an option screen. Click on Troubleshoot option.
    Windows 10 Troubleshoot screen_1
  3. Next, click on Advanced options and then select System Restore.
    Windows 10 Advanced Option_1

Perform System Restore

  1. From the System Restore window, click the Next button.
  2. Windows will shows the most recently created restore point. To view all the available Restore Points, click on the “Show more restore points” option.
    System Restore Point Select
  3. Now you need to decide which Restore Point to use.  I would recommend starting with the most recent one first.
  4. Select a Restore Point and click on “Scan for affected programs” button. This will show you all the programs that are affected (uninstalled / reinstalled) if you proceed with this system restore.
    Confirm your System Restore point
  5. Click on Next. Read the confirmation message and click on Finish.

Windows will take anywhere from a few minutes to an hour to complete the system restore process.

If the CLASSPNP.SYS error gets resolved, you don’t need to do anything. If not, try other restore points until the issue is fixed.

Solution 8: Clean Install Windows

This is the least recommended solution to fix the CLASSPNP.sys error. However, if the problem started on a new computer or after you installed the updates, clean installing Window with the latest available version can fix the issue.

Make sure you take a backup of any available data before performing a clean install. You may refer one of our guide explaining  how to install Windows 10 Creators Update from an ISO file.

Conclusion

The common cause of CLASSPNP.sys error is a hardware failure or some corrupted driver. At times, Windows may not be able to detect the hardware properly which may result in malfunction and prevent the system from normal startup.

Try all the all the solutions recommended in this article and see which one sticks on the wall.

Also, don’t forget to tell us the solution helped fix your PC in the comments below.

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