KB4474419 will not install

I had the same issue, with failed installation with code 80004005. Nothing suggested here worked.

Since many people pointed at the Windows hidden partition, I thought that Bitlocker could have something to do with this.

My hidden partition size is 300Mb and the available space was 97Mb.

I suspended Bitlocker and the update installed successfully.

Thanks for the suggestion, but this technique did not work for me. I have tried setting both the System Reserved as active, and then the primary Windows OS partition as active. The updates fail to install in both cases.  For what it is worth, my dual boot configuration involves two hard drives, one with Windows 7 and one with Linux.

I'm sick and tired of Windows expecting to be the only OS in the system.  This has happened on many Window updates in the past.  Have they not learned or just don't care!

Possible solution for dual boot on same disk.

The idea came from Post #23 of the following forum and I simply provide further clarification:

https://www.sevenforums.com/windows-updates-activation/418834-unable-install-kb4474419-win7-x64-ultimate-3.html

I run Clover to dual boot (legacy boot) MacOS X (hackintosh) and Windows 7 on the same disk with MBR partitions. Initially marking Windows partition as Active caused me problem because the system failed to boot and I had to run Gparted to remove the 'active flag'. Then I remembered when I set up Clover to boot Windows, I needed to select the System Reserved partition (Windows) in order to work. So next I marked the System Reserved partition as Active and the system booted directly to Windows bypassing Clover. The update KB4474419 then went through successfully and subsequently KB4493472 as well. Finally I removed the active flag from the System Reserved partition and everything is back to normal with Clover menu coming up where I can choose to boot Windows or MacOS. I didn't bother to change the MacOS partition back to active as it doesn't seem to matter.

So in my case, it is a simple change without the risk of corrupting the original boot loader already installed. Hope this may also work for others.

I am familiar with the process you described and know that it works for many who are dual-booting. The issue I have, as do some others who dual-boot, is that selecting to boot the Windows disk directly from within the BIOS fails. You end up with a GRUB rescue prompt. For some reason, the dual-boot setup we have requires the Windows installation to boot from GRUB. Windows will not boot without it in our case. Now I am sure this can be corrected by repairing the MBR using a Windows rescue disk, but I know from past experience that this will likely damage the GRUB bootloader, requiring that it then be reinstalled, which is straightforward enough, but my point is that it should not be necessary. A fully booted Windows should install the required updates, no matter how the OS is booted. This is something Microsoft should fix.

When you install the April update that includes the monthly security rollup, I would not be surprised if you have to go through the same process you did to get the March update. Again, this should not be necessary.