Installation of Windows on USB Drive fails

[TechnoMax]

Yes, the culprit was Acronis Active Protection (installed on both PCs, which I normally do not do, I rather use AOMEI or Macrium Reflect and have never had problems with both). After deactivating my external harddisk could be used for a clean Windows 10 install (but it took ages of course, not beeing a modern SSD!). Thanks!