Hi phippy,
The main issue is upgrading to Windows 8.1 from Windows 8 with error 0x80070004-0x2000d, right?
Please take the following steps to have a troubleshoot:
1. Run "dism/online/cleanup-image/restorehealth" to check the health of system files.
2.For the upgrade to Windows 8.1 issue, we could refer to the folowing link to have a fix.
Common Windows 8 to 8.1 Upgrade problems.
http://answers.microsoft.com/en-us/windows/wiki/windows_8-windows_install/common-windows-8-to-81-upgrade-problems/913bbc8e-7280-4858-b303-a123a4065414
3.If the issue persists, this error usually occurred during the migration process which is related to the user profile.
We could navigate to Control Panel\All Control Panel Items\System\Advanced system settings\Advanced\User profiles
Login with these accounts(Except defaultAppPool and Administrator account) and ensure they could work well. We could delete the corrupted user profiles.
Then login with the built-in administrator account to do the upgrade to have a check.
If the issue persists, please check the setup*.log (C:\$windows.~bt\Sources\Panther\ )for more information to troubleshoot this issue. If you have any troubles in analyzing the log, please upload it to OneDrive and paste the link here.
Best r