HP Z800 killed with KB5066835 that cause boot failure, "A Disk Read Error Occurred" if you uninstall

[akierum]

Today after KB5065861 the Z800 is not booting again. This time there is no error.

The FIX is same as previously, I restored 100MB partition and in no time it's working again. Need I explain updates are installed and PC is working as main partition with WIN11 is not touched.

Seem Microsoft wants desperately to brick old PC's. 

[vanadu]

Thanks again. I'm going to clone my backup W10 to my SSD again just for good measure, then I'll upgrade to W11, turn off Windows Update in Services and Group Policy, make a backup of the fresh W11 build, and if boot fails again, use your method to restore the boot partition. Sounds like a plan 👍

[DGroves]

you might want to consider a clean install of win 11 (or win 10) if having issues

updating from 10 to 11 can in some cases have subtle issues that are not present for a clean (from scratch iOS install)

the HP z800 does not meet the MS hardware requirements for CPU or TPM), and as such requires a modified installer that bypasses the hardware checks you can create such a windows 11 install using the program "RUFUS" that will read the official MS win 11 ISO and create a modified USB key OS Installer

[SDH]

DGroves, been doing that... Rufus latest version 4.11 being used, properly configured. About 7 clean installs from the 25H2 .iso (not-in place upgrades). I have enough tenacity for about 2 more tries.

Close to narrowing down which Microsoft updater is borking my clean installs on my testbed Z400 but don't think Microsoft will be interested in fixing the issue. 

[vanadu]

SDH, maybe MS isn't interested in fixing it, but maybe they don't even know about it. On the other hand, someone must know about it because ChatGPT did know about it, as evidenced by Akierum's earlier post, and ChatGPT can't do anything but regurgitate what some human already knows and has published info about somewhere. How could we report the issue to MS? 

On a related note, I tried to clone the System Reserved folder from my backup W10 install to the active W10 install using xcopy from the command line, because Akierum had suggested this as a fix for the W11 boot fail problem. The backup HDD had the original versions of bootmgr and the \boot folder dated 9/10/2025 which is when I created the backup. The new SSD had newer versions of bootmgr and the \boot folder dated 11/12/2025 when Windows updated itself.  Everything else in those folders had the original date stamps. But after overwriting those files from the backup HDD to the SSD, the SSD boot failed with the blue Recovery screen and an error reference to some memory address. This should have worked. Akierum, any idea why it didn't? I didn't clone that partition as you did, but xcopy'ing the changed files should have had the same effect.

I got the SSD W10 install to boot again using the 'Fix boot record' option from the Macrium USB tool. It updated the \boot folder contents, but not the bootmgr file. Inside \boot, the only thing with a new date stamp is BCD. 

I'm including all this because I'm trying to reconcile Akierum's fix with what SDM is experiencing. Akierum seems to be saying it's a boot record problem that has nothing to do with any drivers or other contents of /Windows. If that's the case, then the issue must be in the boot record and should be easily fixable by identifying the offending file and overwriting it with an earlier version. The other possibility is that I'm missing something or my logic is flawed and it certainly wouldn't be the first time for that.

BTW SDH sounds like you're running out of tenacity which would be terrible for the Zx00 community. Maybe this issue will resolve itself or can't be solved by identifying the update build. Maybe we need to identify the offending file within that update. Maybe a diff of the pre- and post-update would be helpful. I don't know...just trying to brainstorm here a bit. 

[DGroves]

all i have is z820 at this point in time and it's unlikely i will acquire a older HP workstation so i can't help other than to recommend you use a HD application or the windows tool to resize the MS partitions and increase the recovery partition if it's not 640meg or larger if you have a 100meg partition that's the EFI partition that should not be there as the Zx00 workstations are PRE UEFI and should only have 3 partitions  that a legacy install creates

Windows 11 KB5066835 has caused a variety of issues for some users, from keyboard and mouse problems in Windows Recovery to performance issues and file explorer glitches.

i would skip KB5066835 and install the later Cumulative Update KB5070773 all by itself no other updates added as i have found that doing multiple updates with KB5070773 will most likely cause KB5070773 to fail

[akierum]

"On a related note, I tried to clone the System Reserved folder from my backup W10 install to the active W10 install using xcopy from the command line, because Akierum had suggested this as a fix for the W11 boot fail problem."

I said clone a win11 boot partition known as 100MB partition on you disk from a non updated win11 install.

Using Win10 partition on Win11 will not work.

[vanadu]

"Using Win10 partition on Win11 will not work."

Yes, I understand that. I'm working in Windows 10 right now. I restored my W10 build from backup after W11 crashed my system. But W10 updated itself yesterday too, and after that I could not boot to W10. The symptoms were similar to the W11 issues. So I tried to xcopy the files in the System Reserved folder from the W10 I had on a backup HDD to the current W10 build on the SSD. I only copied those files whose datestamp had changed after the update. But it would not boot and I had to use the 'fix boot' option from the Macrium live USB. 

I'll try to upgrade to W11 again in a couple days once I've fixed the grub dual-boot bootloader.

[SDH]

Made the breakthrough for clean install of W11 25H2 on ZX00 workstations, and it was painful. The process of elimination and tolerance for strange behavior by BIOS and the installers paid off. I'll post more details tomorrow, but the basics are as follows:

1. Microsoft has a bad security update, shown below, and the workaround is to "hide" that single one using the older MS utility wuhideshow.cab. That program can reach out to the Windows Update servers, see what updates are available for your workstation, and will let you choose 1 or more specific update(s) to hide before you run those updates so later when you actually do run Windows Update it cannot see the hidden ones. Added finding: It turns out that a "Security Update" can have more in it than what we'd think of as only security related.

2. The W11 25H2 Rufus 4.11 installer works well when it is properly set up for creation of the Rufus thumb drive. I therefore have two thumb drives... one for MBR/Legacy BIOS workstations like the ZX00 and earlier, and another for the GPT/EFI or UEFI workstations like the ZX20 and on. "EFI" refers to HP's early work towards true UEFI and is also is present in the Elite 8300/Pro 8300 BIOS of business class PCs, and on. I use the Rufus 4.11 GPT/UEFI version of the thumb drive on those instead.

3. I've found that the target SSD to install onto should be presented to the installer as a fully unallocaded drive, and that should be ideally performed on another computer. I use Microsoft's built in DiskPart utility to accomplish that as detailed in the PDF I attach to a later post here (see page 4). I found this out after I confused the W11 installer (or CMD) by using Shift +F10 to launch an elevated CMD inside the W11 25H2 installer USB and ended up erasing my Rufus USB (twice) instead of the intended target SSD. I had carefully entered the DiskPart commands correctly both times and yet the wrong drive got "cleaned".  The W11 25H2 installer can work with a fully unallocated drive... you just need to be willing to give it a little more time.

4. Earlier in this post I bought up use of a HP SoftPaq to install older ZX00 RSTe drivers versus what the W11 25H2 installer provided. It turns out when you correctly hide of the one security updater shown below you can just keep using the later storage controller driver that the W11 25H2 installer already gave you. That probably is not an RST"e" drivers but if you want the older "e" drivers that older HP SoftPaq I gave the download link for is available.

5. This whole process is a bit fiddly, but my >12 failed clean installs finally led to the right steps that work every time if carefully followed. It is obvious that W11 25H2 likes GPT/UEFI workstations much better than MBR/Legacy BIOS ones.

Here's a couple of pictures showing the available updates via Windows Update as of today, plus show the one to hide. Don't forget to run Windows Update after you hide that single KB so you get all the others:

Here are the Storage Controller drivers from the W11 25H2 install while disconnected from the internet, and these remain after I reconnect and run Windows Update. I don't use RAID so I'm sticking with these rather than using the older RSTe (e = Enterprise) ones (which all the HP workstations are licensed for). EDIT: DGroves later in this post explains the difference.

Finally, here is how I prep the Rufus 4.11 program to create the appropriate MBR/Legacy BIOS bootable W11 25H2 installer from the lates MS .iso. On the Rufus options page that opens after you click on START I check all the boxes except the very bottom one. The entire W11 25H2 install is done disconnected from the internet. I also install my nVidia drivers during that time because the video card is just running on the very basic driver the installer has. EDIT: I choose Custom install and then choose Clean install of the nVidia driver package, and deselect the bottom two parts and only install the actual driver. Been doing that for years and get only the good parts that way. My reconnect to the net is done, I confirm via the taskbar icon that I'm connected, and do that right before launching wuhideshow.cab. That is done that Window Update is not able to get ahead of your hiding of KB5068861 first.

Here is how I use Rufus 4.11 plus the MS .iso to create my installer thumb drive:

[akierum]

Good job on sharing Rufus config for those that don't know how to do it. 

I tried the wuhideshow.cab too, but hidden updates would still download after a while and brick system. Update KB5066835 is cumulative and these can't be blocked, ChatGPT confirms this.