Windows 7 boot stalls at classpnp.sys

I know this is a very old issue but I haven't seen any solutions.  Is there one? 

This has happened on my Thinkpad X61s sporadically after upgrading from Vista x64 Ultimate to Windows 7 x64 Professional.  There seemed to be a connection between motherboard temperature (hot after installing Win7 and updates) and the boot failure, but I am not 100% certain. It happened several times under various conditions including immediately after a successful full install and also after an install and  OEM driver installation.  Sometimes simply waiting and then restarting got it to boot.  Other times not. 

The boot would stall immediately after the first two dots of the logo appeared and then froze.  Booting to safe mode showed that the boot stalled at classpnp.sys.

I tried all the usual stuff like system repair.  No improvement. After letting the system settle(ie., cool) and also flashing the BIOS (it was very old), it hasn't happened again but I am worried. I see lots of references to this exact issue but so far no solutions.  Someone always suggests a system repair, but after the OP reports that didn't solve it (it also didn't in my case) the thread continues with others saying they have the same issue and then just dies.

So.... has there been any progress determining why systems fail to boot, stalling at class.pnp.sys? 

Paul

 

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Last updated September 12, 2019 Views 109,489 Applies to:

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Hi Paul,

What steps you have tried other than system repair?

Let’s follow these methods & check if it helps.

Method 1

If you have any unnecessary external device connected to the machine, you may unplug them & check if you are able to boot to the desktop.

Method 2

You may try to boot to the installation disk and verify if you are receiving the error.

Method 3

You may try to run chkdsk from Windows Recovery Environment & then try to boot to the desktop normally. 

a.Follow the steps from this link to boot into Windows Recovery Environment and open the command prompt. For more information, follow the section  ‘To open the System Recovery Options menu on your computer’  from this link.

b. In the command prompt window, type ‘chkdsk /r’ and press Enter.

 Note: During the restart process, Windows checks the disk for errors, and then Windows starts.

Hope the information helps. Please post back and let us know.

Regards
Debleena S
Microsoft Answers Support Engineer
Visit our Microsoft Answers Feedback Forum and let us know what you think.

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Unfortunately, I have done all of what you suggest.  This is a laptop, and it has failed to boot immediately after an install with nothing external connected as well as later in the install / configure process.  It does not always refuse to boot.  When it will not boot, System Repair (run from the DVD) has announced that there is a problem and it cannot fix it, although it does not state what the problem is.  Memory test shows memory is OK.  Checkdisk (which runs successfully during system repair) shows the hard drive is OK when run from within Windows (when it boots). At one point I totally wiped the hard drive, reformatted, and installed.  During that process, it refused to boot at least once.

The last time it refused to boot was when I realized it was hotter than usual (but not dangerously hot), so I let it cool a couple minutes.  The next attempt booted OK and it has booted OK ever since.  So far.

Note that Vista x64 ran 100% perfectly for a couple years on this same machine.  Additionally, my copy of Win7 is an upgrade copy so although it does a clean install over Vista (Vista is Ultimate, Win7 is Pro so it will not actually "upgrade") it does not actually reformat the hard drive.  Is that a clue?  Is there something remaining from the Vista install that is confusing things? The next boot after a failed boot offers the repair option.  If I take that, it announces something like "a required device is unavailable".  That sounds like something like the hard drive has gone missing.  But it is reading the hard drive (the boot actually begins, it just stalls).

Like I said in my original post, it is currently booting OK.  I have flashed the BIOS and finished all driver installation.  I am merely worried that I have not in fact fixed it since this is a very common problem, reported by many people over the last year or so.  Some of them were using brand new machines with the factory Windows 7 load.  I am merely wondering if anyone has found the real issue and if there is a permanent fix.

I know everyone is trying to help, but if you look at the many threads reporting this problem (stalling on classpnp.sys) running repair and checkdisk etc. NEVER fixes it.  The threads just die out without a solution. 

BTW, MS needs to look at the code for this web site..... using Firefox, there is no cursor when typing, making it very hard to make corrections.  

Paul 

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Interesting.  Did some more digging.  Turns out that while everyone seems to think the boot is stalling at classpnp.sys, it is in fact stalling at the NEXT file in the boot sequence, which is cdrom.sys (in my case, anyway).  That makes a bit of sense.  In my case, there was a DVD drive while I installed and configured.  It was in a docking base.  In normal use, there is no dvd drive (it is a Thinkpad, which has no internal drive), and if I configure a boot log, the system reports that cdrom.sys did NOT load.

Given the fact that when it failed to boot the repair option claimed that the boot failed because a resource was not available, perhaps the BIOS was reporting a cdrom was available but the system could not find it?  

But I'm just guessing.  I wish that Microsoft would weigh in on this one.  It has been going on for a long time if you Google for it.  

Paul 

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While in the Safe Mode click the Start button and then click Restart.  It will restart in the normal operating mode.

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While in the Safe Mode click the Start button and then click Restart.  It will restart in the normal operating mode.


Yes......  And the point is?

Paul

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OK _ I ran into this problem today. Apparently classpnp.sys is a Microsofts SCSI driver but the problem was to actually get to the root cause of this problem I had to turn off automatic reboot on system hang in the F8 startup options. Nothing else I tried geve me a reasonable lead to an answer. I could not get into safe mode, but I could try startup repair but this didn't help as the problem is a hardware driver, not software.

Eventually after turning off automatic reboot I got a BSD which at least pointed to the driver for my Atto Celerity Fibre card being the culprit. Removing this card allowed the system to boot normally. Either the card or driver is corrupt but ... at least I have a place to start.

In my opinion this insane urge to "hide" problems from the user has led to this being one of the most difficult problems to track down, even for a savvy computer user like myself. Microsoft need to develop a reporting system tha tinforms hte user exactly where hardware problems lie - in htis case a log of the failing driver that popped up on the next boot would have been sufficient to identify the problem hardware. So simple and yet so obtuse - Microsoft hit yourself over the head with a 2x4 at least 10 times until the message gets through - abstraction layers are no good when problems are involved.

I'm pretty sure what is happening is that classpnp.sys actually loads any third party SCSI drivers like raid cards, fibre cards, legacy CD drives etc - that is what makes this a difficult problem to track down. Could be a failing hard drive, a dead CD ROM controller or a problem raid card etc

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Not sure your issue is quite the same.  In the scenario I am describing, the boot simply stops at the step AFTER reporting that it has loaded classpnp.sys.  In my case, that would be loading CDROM.SYS.  No automatic restart and no BSOD.  It just stops dead in its tracks until you hit the reset button.  But I fully agree with you that in this day and age of smart OSs, it is inexcusable for any OS to be as obtuse as this.  It should be simple to add a subsystem to keep track of what the system wanted to do, whether it in fact did it, and if not, what prevented it.  Like it is supposed to do with standby issues. 

FWIW, it is now several months later and after I updated my BIOS, the issue has not returned.  I do think your issue and mine are probably related, though. 

 

Paul

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Hi Paul,

Let’s follow these methods and check if it helps.

Method 1

You may contact your computer manufacturer and try updating the BIOS (Basic Input Output System) then check if the issue persists.

Note: Modifying BIOS/ chipset incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/chipset can be solved. Modifications of the settings are at your own risk.

Method 2

You may follow the steps suggested in this link and check if the issue persists.

http://social.technet.microsoft.com/Forums/en/w7itprogeneral/thread/566cdd43-ce91-4e64-93e0-8d09d8fc1ea0

Note: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. Microsoft does not control these sites and has not tested any software or information found on these sites; therefore, Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there.

Method 3

You may also follow this link and check if the issue persists.

How to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows

Hope the information helps. Please post back and let us know.

Regards
Debleena S
Microsoft Answers Support Engineer
Visit our Microsoft Answers Feedback Forum and let us know what you think.

 

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mu pc will not even make it to the system recovery menu.

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OK _ I ran into this problem today. Apparently classpnp.sys is a Microsofts SCSI driver but the problem was to actually get to the root cause of this problem I had to turn off automatic reboot on system hang in the F8 startup options. Nothing else I tried geve me a reasonable lead to an answer. I could not get into safe mode, but I could try startup repair but this didn't help as the problem is a hardware driver, not software.

Eventually after turning off automatic reboot I got a BSD which at least pointed to the driver for my Atto Celerity Fibre card being the culprit. Removing this card allowed the system to boot normally. Either the card or driver is corrupt but ... at least I have a place to start.

In my opinion this insane urge to "hide" problems from the user has led to this being one of the most difficult problems to track down, even for a savvy computer user like myself. Microsoft need to develop a reporting system tha tinforms hte user exactly where hardware problems lie - in htis case a log of the failing driver that popped up on the next boot would have been sufficient to identify the problem hardware. So simple and yet so obtuse - Microsoft hit yourself over the head with a 2x4 at least 10 times until the message gets through - abstraction layers are no good when problems are involved.

I'm pretty sure what is happening is that classpnp.sys actually loads any third party SCSI drivers like raid cards, fibre cards, legacy CD drives etc - that is what makes this a difficult problem to track down. Could be a failing hard drive, a dead CD ROM controller or a problem raid card etc


Turning off automatic reboot worked for me.  I had connected an external USB CDROM drive prior to the problems.  During a logged reboot, my HP Netbook hung after that classpnp.sys.  It would appear that the automatic-reboot-on-hang was constantly rebooting the thing.  Once off, I was able to get past the hung driver and boot up.  Now to blow away the hung driver...

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