During boot press F9 or if its F10 to display boot options, try from there to select your usb CD/DVD-reader?
Also in advanced settings in bios you can select which boot sources should be identified during boot, make sure you didnt disable "Optical" or such in that list?
Some progress, With Win7-64 Premium Install Disk in CD/DVD reader....
- Unplugged NUC
- Plugged NUC back in
- Ran Setup
- Set Legacy Boot and found Internal 2.5 " HD and
- Legacy Pioneer CD/DVD reader attached via USB3
- Booted CD and attempted fresh install (Custom)
- Install warned that It would not install to HD because BIOS did not assure that it would boot the partition...
- Went back to Setup for Bios and enabled UFEI boot devices.
- Forced boot to Legacy CD/DVD
- Attempted Win7 -64 install....
- Install appeared to begin correctly without balking about partition/bios problem......
Were you able to fix your issue?
Are you having problems with the NUC recognizing USB devices?
Have you tried using any other USB device?