Here at school, and at my home, we use an SSD for the OS and programs, and a traditional HDD for user files and data.  This requires a registry edit before a user logs on, and has worked great to save SSD space for those items that need SSD speed.

However, it appears to cause issues with major updates in Windows.  While minor updates happen frequently, major ones always fail.  I needed the major upgrade to 21H2 to make Starfall work, so it was a priority!  🙂

To fix this issue I had to do the following.

1.  Logon with the admin account that was originally setup with windows.  This account is stored in the User folder where windows was installed.
2. Undo the registry hack to put user folders on the D: Drive.
   1. [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList] should be returned to %SystemDrive%\Users
3. Run the following in an administrator command prompt.  In short, it repairs the Windows installation folder.
   1. DISM.exe /Online /Cleanup-image /Restorehealth
4. Now I ran an upgrade from a flash drive with the current Windows release…and it worked!

Hope this helps anyone else with Windows upgrade issues, or more importantly, Starfall issues!