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Windows 7: drive letters switched after changing motherboard

02 Apr 2010   #21

Windows 10 Pro x64 x3, Ubuntu

Just a thought, does the re-boot happen with safe mode - it could be a relatively simple driver issue if you can get into safe mode

My System SpecsSystem Spec
02 Apr 2010   #22

windows 7 ultimate

I can get it to safe mode, and I find that it halts on the classpnp.sys file and then reboots.

I found this after doing a search
"I had this same problem and solved it by changing 2 BIOS settings. This is an eMachines T2245, don't know what the motherboard is, you can look it up if you want to:

1. Disable CPI APIC support
2. Under PCI/PnP settings, set Plug and Play O/S = YES.

I don't know if both are necessary, just know that after making these changes the PC boots in Win 7. I believe it is build 7600.

Good luck, hope this helps some of you."

but it didn't help.

3 days at this.
My System SpecsSystem Spec
02 Apr 2010   #23

Windows 10 Pro x64 x3, Ubuntu

Just had a quick trawl around the technet and found a few problems with the classpnp.sys file.

you may want to try a sfc /scannow from safe mode and see iif that helps (Note after the repair if successful it may take a while to boot the first time so may be an idea to grab a coffee at the opportune moment)

Have attached a copy of a good file (from win7 pro x64 rtm ) which may be an option to just replace the original file you have

Attached Files
File Type: zip (85.7 KB, 0 views)
My System SpecsSystem Spec

02 Apr 2010   #24

windows 7 ultimate

1:30 in the afternoon, and I admit defeat. For whatever reason, you have to do a fresh install of Windows 7 each time you change your motherboard (if the drive letters get transposed). I probably tried 10 to 20 different ways of getting this to work, and as far as I call if your system reserved gets deleted or transposed and your primary is transposed you're screwed. Lesson learned here. I just installed a new install of windows 7 alongside of my existing copy and the old copy was renamed c:\windows.old. Contained all of my files. Now I'll just go about cleaning up.

Completely frustrating experience.

quick edit. Cheers Nigel. I saw your post just after mine. I wondered if there were bad blocks on the disk also, but I've scanned with chkdsk and a 3rd party utility and everything looks ok. Not sure why what happened, happened but I've been wrestled to submission.


My System SpecsSystem Spec
03 Apr 2010   #25

windows 7 ultimate

Ok. The next day. For anyone who stumbles across this post, the way I stumbled across this site looking for answers. Take heart. I'm about 100% sure the problem was and is the Asus P5N-D. It's a hardware issue addressed somewhere within the code, and you can't solve it the way I went about it.

I used diskpart, deleted the system reserve wiping out the BCD info (after trying about 30 times to get RE to fix it on it's own). Then used diskpart again, created a partition, assigned a letter (with DP), marked the partition containing windows as active, used bootrec /fixboot, bootrec /fix mbr, bootrec /rebuildbcd and bootsect.exe /nt60 C:. No result. I tried using an exact match to the drive (1 TB seagate) and installed a fresh copy of 7. Then copied the working bcd info while using the rescue disk command prompt, onto the non working boot section (system reserved), making sure to again add the correct attributes. No good. I tried installing from a month old windows image creating just the c:windows and z:\boot. No good. Tried marking the partition as active. No good. Tried switching drive letters and running bootrec commands. No good.
I think that's about it. (Oh and verified it wasn't a sfc or crc problem on the original. That about covers it. 3 days. probably 40 hours. And no way it works. You have to do a fresh install of 7 if you change your mother board (at least with sata). Any question, please feel to pm me and I'll try and answer some day.

If your down, RE is not going to help you. It'll tell you there's a problem booting, but that's about it. You'll see and error in the classpnp.sys in a safe boot, but ignore it. Again, it's a hardware incompatibilty issue. Personally, I think MS did a crappy job on this version on Windows. Making it so you had to either do a clean install if your system no longer booted. It's crazy. The option for a repair install is only available from within a working 7 os. You can't use easy transfer because the system is unavailable so you lose your setting. You can't your disk management because it's only available from a working OS. You lose everything if you can't boot. Even if you've been diligent and had Windows 7 image files, or complete copies of the partition (ACronis, Norton, etc.). It wouldn't matter because they're unusable.

My System SpecsSystem Spec

 drive letters switched after changing motherboard

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