[SOLVED] Windows 7 hang on boot (Classpnp.sys)

Published February 16th, 2011

Windows 7 hanging on boot? Safe mode gets stuck at Classphp.sys? Here is the solution.

This appears to be related to an AHCI/IDE driver update which renders the PC unbootable.

Here is a solution that works on Toshiba Satellite laptops:

1) Power on the laptop
2) Press F12 key to enter the BIOS
3) Go to "Advanced" menu
4) Go down to "System Config"
5) Change SATA Controller from "AHCI" to "Compatibility"
6) Press F10 to save and exit

Your laptop should now boot into Windows 7 and you should run windows update and make sure all of your drivers are up to date.

If you need a new copy of Windows then using this link will help to support this website:

Cheap Windows 10

At 2012-06-15 17:55:00, Daniel Vengoechea left the following comment ...
It did not work on my lenovo machine. It still shows classpnp.sys and stucks there for life any ideas? [email protected]

At 2012-06-16 23:02:00, Chris Newland left the following comment ...
Hi Daniel, What model Lenovo? What was the last thing you did before it stopped working? In my experience and from what I've read online it is nearly always caused by a Windows Update that breaks compatibility with the PC's hardware. Very occasionally it is caused by a loose hard drive cable.

At 2012-06-19 09:12:00, Humphrey left the following comment ...
Hi, your solution fixed the problem on my Lenovo G550. I also replaced the classpnp.sys file before re-configuring the BIOS. For sure this problem is due to a Windows update as it stopped booting from one day to another without installing any new devices on the machine. Thank you very much for your advice.

At 2012-06-20 21:28:00, LC left the following comment ...
I have a Sony Vaio and it's bios doesn't have the option sata controller on system config. How can i change it?

At 2012-06-22 00:42:00, Frank left the following comment ...
Thanks ...it work!

At 2012-07-09 09:52:00, Lucas left the following comment ...
How do i solve this issue on HP Compaq 6720s because it does not those options on the bios?Please help

At 2012-07-13 06:06:00, Marcel left the following comment ...
Had the same hang issue and found that the OS installed by supplier was 32bit not 64 so it didn't like 8gb of ram, after taking out 4gb of ram it booted.

At 2012-07-13 08:28:00, Prd left the following comment ...
hey friends, Thankx i have a new lenovo Z370 and i tried the steps as you directed but didnt solve my problem. Is a new laptop and was just installing normal softwares to make it for everyday running I think lastly i installed a Blackberry Desktop Software 6 I doubt the problem would have occured by this as it creates the installable files for Microsoft 2008+ redidtributable openly in the c: and it had an install.exe file ......... but i removed the HDD and deleted those files too but didnt solve my problem Please anyone can help me, I appreciate and wud be greatful The problem is the same hangs on claspnp.sys

At 2012-07-15 06:09:00, Gus Helton left the following comment ...
I have a Gateway PC with Win7 64-bit and had the same thing happen. Tried everything, no success. Tried what you suggested but my BIOS did not have the 'compatibility' option, so I switched it from AHCI to IDE. It worked. Booted just fine, Windows ran CHKDSK and found a handful of errors in some indexes, and after a reboot works great. I'm not a whiz so I don't understand what I did or what went wrong, since the BIOS has been set to AHCI for over a year with no errors before.

At 2012-07-16 11:28:00, Daniel left the following comment ...
Hey there,i have a Samsung HP R540 Notebook Laptop with the same issue, i cant use safe mode nor startup repair nothing at all without blue screen of death appearing. Anoher issue is if i press f12 it comes up with a lot of different copyright stuff then says PXE Media test Failure, Check cable. Im stuck on what to do please can u help

At 2012-07-16 11:33:00, Daniel left the following comment ...
I mean my laptop is Samsung R540

At 2012-08-01 14:28:00, Gene Savory left the following comment ...
My AMD dual core gets hung up during boot at "loading windows." 10 minutes later it reboots, and offers to repair, but the repair never works, so I select "start windows normally" and it will boot to windows. Offers to find solution never work. Safe mode boot stops with "Loaded: \Windows\system32\drivers\CLASSPNP.SYS" No hardware changes made. Was fine for months, and then (update?) started this behaviour.

At 2012-08-20 14:00:00, Nav left the following comment ...
I have the same problem. My laptop is acer Aspire 5745G. It just stuck on "Starting windows" screen. If I boot in safe mood, it just stuck or hang with classpnp.sys for life. I have tried every things & spent about 3 days to fix this error but been unsuccessful. Please help.

At 2012-08-22 06:19:00, Max left the following comment ...
Omg. thanks you. It worked. I tried everything. Fix boot, check disk. Very grateful.

At 2013-01-07 16:31:00, Servando Pardo left the following comment ...
Thanks, this fix works for me.

At 2013-01-27 01:13:00, Boffill left the following comment ...
I hope this will fix my problem. I'm afraid to restart my PC because I might get stuck at the Windows Logo again. Whew.

At 2013-03-01 12:33:00, Chris Smith left the following comment ...
Nice one - many thanks!!!! This worked on my Lenovo T61 after installing a Samsung 840 Pro. Was banging my head on the wall for hours beforehand thinking the new disk was problematic.

At 2013-05-16 08:50:00, Mark left the following comment ...
Great, this solved my problem too : a reboot and windows repair could not fix it with error 0x8000FFFF. after chancing BIOS to ACPI it worked !

At 2013-05-31 17:37:00, Bill left the following comment ...
This worked with my Dell Latitude e4310

At 2013-06-20 23:52:00, michael left the following comment ...
hi everyone. Its now the second laptp I have had to fix with this issue. First was my wifes toshiba and the above mentioned repair steps worked fine on it but now on an asus belongings to my motherin law its not working. recently windows undated the framework files etc etc could it have been that that is giving the classphp.sys error? can anyone help me on this. to make matters worst the asus does not have any restore points on it .

At 2013-07-07 19:07:00, sachin left the following comment ...
Hi, I am using Acer Aspre 5570z Laptop, my laptop getting hang during startup. Its shows starting window when I select repair mode. In safe mode it hang after CLASSPNP.SYS file. I inserted installation DVD but again it hang after loading library files. Please help me.

At 2014-10-21 23:35:00, Tony left the following comment ...
Worked for me, Thank you so much for your help and for taking the time to post this information. I tried starting windows normally at first and it didn't work so I chose the other recommended option of letting windows check for errors, then it restarted and went to the same screen with the same two options so I chose to let windows check again, then it restarted again and after a minute or two it went into system check, it also done this twice and then thankfully it booted up properly and then automatically updated the new drivers it needed for the configuration changes.

At 2014-12-13 16:52:00, Daniel left the following comment ...
Nice save for me. I had just replaced all the hardware in my old pc, and had not used my HD for over a year. How nice to have a solution :)

At 2015-02-05 00:21:00, Samsung R540 laptop left the following comment ...
My Samsung was freezing up so I tried to do a basic restore it did nothing so I did a complete restore and it went thru and finally restarted and kept going to the WINDOWS ERROR RECOVERY screen and nothing works safe mode nothing it stops at CLASSPNP.SYS. I do not have a disc for it because it did not come with one, I had the same problem before and restored it, and it worked fine. Any suggestions would be great. My tech knowledge is I know how to turn it on but that's about it, I can tho follow directions if you have any ideas. Thanks You.

At 2015-08-18 16:55:00, Eskiso left the following comment ...
If that doesn't work, since what comes next to clsspnp.sys is the cdrom.sys try unscrewing the CD/DVD-Rom, and try it without that.

At 2016-04-08 08:56:00, The IT guy left the following comment ...
Thanks OP this worked! User was doing updates and after restart this happened. Laptop was Lenovo T500.

At 2016-08-11 14:30:00, Chinmay left the following comment ...
Thanks a lot..!!! It worked, I had set my bios settings to default so the windows was unable to start. By changing SATA controller from 'AHCI' to 'IDE' it worked. Good solution.

At 2016-11-23 08:00:00, Sumo left the following comment ...
Amazing, This worked with my Toshiba laptop as well. any thanks.

At 2016-12-09 23:21:00, Akis left the following comment ...
Well for me it was just the cable i think...just swap places and done....!!!Ty mate

At 2017-05-13 16:29:00, Agar left the following comment ...
Lenovo ideapad 300 does not have any hdd-related changing options - back to win10 :(

At 2017-10-23 06:35:00, Hemant Ghiya left the following comment ...
Thanks all, it worked for me for dell1510 laptop. I changed AHCI to AHC.

At 2017-10-25 09:39:00, Kaupo left the following comment ...
This solution worked on my Dell Latitude E4200. Thank's a lot!

At 2017-11-13 23:27:00, Grateful Toshiba user left the following comment ...
It worked for me on a Toshiba Satellite Pro, I had changed the drive from normal HDD to SSD, and got this error. Changing to compatibility in the BIOS fixed it.

At 2018-03-05 09:12:00, Carmine DG left the following comment ...
Thanks Man, workstation in my workplace had this problem, due to power loss, changed AHCI to IDE and back to life... Thanks MAN

At 2018-06-29 20:16:00, Susan NJ left the following comment ...
Thank you for this excellent fix! This worked for me on an older, but needed Dell Latitude laptop.

At 2018-08-06 19:34:00, Alyssa MI left the following comment ...
If you boot in safe mode and then restore your computer to the state it was before you attempted the updates it will boot fine. Sift through your available updates and pick out the needed ones. This problem occurs because the updates are not compatible.

At 2018-08-29 15:45:00, Shane left the following comment ...
I got this issue after a windows update on 8/28/2018. I disconnected my blue ray drive from the SATA port and was able to boot into windows. HUGE thanks to the people that pointed out it was the cdrom.sys file and not classphp.sys file it was getting stuck on. Answer me this though; why would Microsoft program safe mode to show the drivers successfully loaded instead of the next driver it's trying to load?. Do they not want people to have a good experience with their product?

At 2019-03-28 19:37:00, daffy688 left the following comment ...
This solution worked like a charm!!!! Thank you so much!

At 2019-09-30 10:55:00, rickjames left the following comment ...
apparently on an HP, or a Dell laptop its because it doesn't like the 8Gig ram, switched back to 6Gig and it booted perfectly fine. but thanks for the post because if helped me find the answer i needed.