Hello AlexanderR, I’m sorry for the inconvenience that you have faced with your NUC.
This behavior looks like a BIOS issue, so I would recommend you to roll back to the previous BIOS version and check if the behavior persists.
If it does, please get in touch with our Warranty Department so they can help you to replace the unit: http://www.intel.com/p/en_US/support/contactsupport
Reverting do bios 0024 did nothing.
One way to solve this problem is to reinstall windows 8.1.
Why would i replace the unit? It's nothing wrong with it. This is a combination of UEFI, intel bios and windows 8.1.
Last time i entered the windows in the same manner the same thing happend.
I have had more problems with the nuc than all my other machines combined.
Can you please get the bios technicians to look in to this? It should be possible to enter the bios without killing the windows installation.
One other thing that is weird.
My msata witch holds the windows 8.1 installation is c:\
Windows was installed on this machine without the Samsung Evo ssd installed.
Now for some reason the Samsung Evo ssd is c:\ and the msata is d:\
If the machine tried to boot from c:\ it obviously won't work now.
Edit: Now for some reason the duplicate entries where gone in the bios and windows 8.1 would boot normaly. Go figure. Just as i was going to install ubuntu.
Intel: Can you please look in to this? I must be able to enter the bios without this happening.
AlexanderR, have you tested the system without using any USB devices? I've seen that some NUCs fail to boot to the main hard drive when an USB device is connected.
You can try also to roll back to BIOS version 0021, just for testing. However, once again I suggest you to replace the unit, if you can.