Matt, if the OS was installed with UEFI and secure boot enable, you should be able to boot to windows. The issue is if you disable UEFI and enable legacy, Windows is not going to boot up.
It looks like the DH61BE motherboard supports Windows 8, we haven’t received the new list including Windows 8.1 Desktop Boards — Supported operating systems
We have been providing this workaround to a lot of customer who are experiencing issue with Windows 8.1. You may want to check it out and give it a try and let me know the results.
1. Go to the secure boot options on BIOS
2. Enable secure boot (if disabled)
3. Check on the option that says “Install Intel platform key”
4. Press F10 to save changes and restart the system