What can I do to make the installer continue and work properly with my setup?
Mova a partição do usuário de volta para C :. Esta é a única maneira de fazê-lo funcionar. A MS avisou você para não fazer isso:
Using ProfilesDirectory to point to a directory that is not the system volume will block SKU upgrades and upgrades to future versions of Windows. For example if you use Windows Vista Home Premium with ProfilesDirectory set to D:\, you will not be able to upgrade to Windows Vista Ultimate or to the next version of Windows. The servicing stack does not handle cross-volume transactions, and it blocks upgrades.
Isto é para o Vista, mas também se aplica ao Windows 8 (.1).