Windows only boots from UEFI

I am having a strange boot error. I recently updated my desktop from Windows 7 to Windows 10 and had zero problems with the upgrade process. My system has a 10 gb Sata drive for the boot drive and several storage drives that were disconnected during the upgrade process.

My boot priority in the UEFI is set to boot from an optical drive first, then the Windows boot manager on my system disk. Every time I attempt to boot I get the error boot mgr missing press ctrl alt del to restart, however, if I select the Windows boot manager manually from inside the UEFI Windows boots normally and everything in the OS works perfectly fine.

This doesn't make any sense to me.

System details:
Asus Sabertooth 990FX R2.0
AMD FX-8320 Vishera 8 core 3.5 GHz
2 X 8GB G.SKILL Ares DDR3 1600 ram
EVGA GeForce GTX 960
WD Green 10 GB Sata drive

You should start by telling us if your system is installed on a drive with MBR or GPT partition table.

Kjmatheis said:

My boot priority in the UEFI is set to boot from an optical drive first, then the Windows boot manager on my system disk. Every time I attempt to boot I get the error boot mgr missing press ctrl alt del to restart, however, if I select the Windows boot manager manually from inside the UEFI Windows boots normally and everything in the OS works perfectly fine.

System details:
Asus Sabertooth 990FX R2.0

You do not need to change the boot order of drives in your UEFI firmware settings, so use the default settings.

If you want to boot from an optical drive, then just use the one-time boot menu.

Boot to UEFI Mode or Legacy BIOS mode

Boot to UEFI Mode or Legacy BIOS mode

Select the firmware mode during bootup

1. Boot the PC. As the firmware starts to run, press the key that opens the boot device menu. For example, press the Esc, F2, (Asus motherboard F8), F9, F12, or other key to enter the firmware or boot menus.

2. On the boot device menu, select the command that identifies both the firmware mode and the device.

Note

You might see separate commands for the same device. For example, you might see UEFI USB Drive and BIOS USB Drive. Each command uses the same device and media, but boots the PC in a different firmware mode.

Thanks everyone, it turns out that csm was enabled in my UEFI and set to UEFI and legacy. Apparently it would default to legacy and try to boot from an old Mbr partition for a Windows installation that no longer exists.