Win10 died on dual boot system, reset fails

I have my HP Pavilion laptop configured as a dual boot system with Windows 10 and Kubuntu Linux. It had been working fine for several months. But something went wrong during a Win10 update, and now Win10 won't run at all. (Kubuntu is fine.) When it starts it finds errors, automatically corrects them, and then reboots. If I go to Reset at that point, the gears whirr for a while and then it tells me that there was a problem and nothing was changed. (I've also tried other alternatives such as the Command Line, with no success.)

I've downloaded the file Win10_1903_V1_English_x64.iso onto a flash drive and tried to reboot from that. The activity indicator on the drive blinks a few times and then I get an unresponsive blank screen with a blinking cursor.

How can I get Win10 started again? I've abandoned any hope of recovering anything from my earlier installation; I'd be happy to just do a reinstall.

Welcome to the forum. What is the disk setup is MBR gpt and what is the boot manager?

pwabrahams said:

I've downloaded the file Win10_1903_V1_English_x64.iso onto a flash drive and tried to reboot from that. The activity indicator on the drive blinks a few times and then I get an unresponsive blank screen with a blinking cursor.

The unresponsive black screen with a blinking cursor means that the USB flash drive is not bootable. You say you downloaded the iso file onto a flash drive. What is on the flash drive exactly? Is it just the ISO file itself? If so, that is not bootable. You have to extract the contents of the ISO file to the flash drive, not just copy the ISO file itself to the flash drive.

Also, what format is the flash drive? Is it GPT or MBR partitioned? Is it a FAT32 or an NTFS partition? If you are trying to boot in UEFI mode and the flash drive is formatted with an NTFS partition, it is likely not compatible. If you are trying to boot in legacy BIOS mode or CSM mode, and the flash drive is GPT partitioned, or the partition is not marked as active on the flash drive, it is not compatible. What did you use to create the flash drive? Rufus?

The flash drive should be MBR partitioned, with a FAT32 partition marked as active, containing the contents of the ISO file (not the ISO file itself). That will be universally bootable in both UEFI and legacy BIOS (CSM) modes.

It turned out that unetbootin doesn't work well for images that aren't Linux images. So I tried creating the image with the tool woeusb, and this time it worked. I wasn't sure it was working since when it got to the point of doing the install, it showed 0% progress for several minutes. But I let it run overnight and woke up to find the Windows 10 install ready to go. I had no trouble installing Win10 from there.

It took me a while to get grub reinstalled as the operative boot loader, though. There probably is a way to get the Windows boot loader to load Kubuntu, but I didn't explore that possibility.