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2,847 Tutorials

How to troubleshoot a slow booting PC

Find the culprit when it's hanging at Windows\System32\Drivers\ClassPnp.sys

QUESTION I upgraded my PC's motherboard, CPU and hard drive. Windows 7 64-bit now takes four minutes to load. By booting into Safe mode, I found that it's hanging at Windows\System32\Drivers\ClassPnp.sys. Malcolm Pott

HELPROOM ANSWER The possible causes and solutions for this problem are myriad. First ensure your motherboard has the latest Bios installed. Next, use the Recovery Console to check Windows and your hard disk for errors.

Boot up from your Windows 7 installation disc and choose 'Repair my computer'. When the 'System Recovery Options' menu appears, choose 'Startup Repair'.

If this doesn't offer any solutions, return to the System Recovery Options menu and select 'Command Prompt'. At the command prompt, type chkdsk c: /f and press Enter. This will check your hard disk for any file errors and repair them as necessary.

If the problem persists, try disabling onboard hardware such as network and sound cards one by one via the Bios. Check whether the machine still boots each time.

Failing this, delete the ClassPnp.sys file. It may be corrupted, and Windows will create a fresh version on reboot. Access the Command prompt via the Recovery Options menu, then type rename c:\windows\system32\drivers\classpnp.sys classpnp.old, press Enter and reboot.

If you're still experiencing problems, a Windows reinstallation is in order.

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