Windows 10 only boots with Disk in Drive - "Insert Proper Boot Device..."

I had Windows 8.1 installed on my SSD.

I tried to install Windows 10 yesterday with an USB Stick and eveything went okay.

When the Installation was done, I got the message

"Insert proper Boot device...".

When I installed it again with a DVD,

"Press a key to boot from CD..."

Showed up and after that, Windows 10 booted normally.

But after I remove the disk from my drive, the first message pops up again.

I can only boot Windows 10 when the Installation Disk in in my drive!

I already tried probably everything:

• bootrec /FixMbr /FixOs /ScanOs /RebuildBcd


• bootsect /nt60 ALL /force


• recovering BCD/MBR with EasyBCD


• Changing the Partitionsystem to GPT...


• Changing the Boot Order/unplug HDD

My Partitions are set up like this:

How can I resolve this issue?