Error: 0x80070003 while updating Windows to Windows 10 1903

Hi Ardispicy,
I am Sumit, an Independent Advisor and a 2-Year Windows Insider MVP here to help.

Apparently an older installation of Macrium is preventing the update.

2019-10-13 11:28:02, Warning SP Failed to get WimMount file version, C:\program files\macrium\reflect\wimmount.sys, 0x80070003

Via the following thread, you would be able to resolve the issue.

https://answers.microsoft.com/en-us/windows/for...

After banging my head against the wall for several days on this issue, I finally discovered this thread on the Macrium forum:

https://forum.macrium.com/Topic28454.aspx

It appears there was a defect in a recent version of Macrium Reflect which fails to restore the path of wimmount.sys image path after uninstalling Macrium.

Fortunately the user in the forum post provided screen shots containing the values of the registry keys if you want to inspect your own system.

Key: Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WIMMount\ImagePath

Old Value: \??\C:\Program Files\Macrium\Reflect\wimmount.sys

Correct Value: system32\drivers\wimmount.sys

I would be merging your older thread that I had split a while ago to this one.