The simplest way to silve this problem is to disable Windows Defender
I have a DM 800 HD that don’t start anymore, the display is black, no led only etherned leds are on and steady, also without cable.
After some search I have find a guru of Dreambox hardware on this forum
and now I am investigating the problem.
Here there is some schematics thata I have find there (Credits to Johnny B)
1) Verify that the disk you want to use for boot is bootable (active flag)
2) use bcdboot to install the BCD (Boot Configuration Data) on your disk