Asus dual boot no choice
 

My desktop is Asus M51AC with Windows 10. I made it through the procedure for dual booting Mint 18. Mint installation seemed to go quickly and without error. But when I reboot the system automatically boots Windows. How do I call up a boot menu for this system? Other installation factors I should look at?

THIS might work.

Your reference is for Windows 7, Ubuntu 14.10. I am using Windows 10,Ubuntu 15.10 so I expect I am UEFI mode. But why doesn't boot loader know 2 OS's or did Mint install fail completely?

If UEFI, you need to get to the UEFI boot menu - just like you did with BIOS. Could be <Esc>, <Del>, <F2>, <F12> ....
The default entry needs to be updated to point to Mint - use efibootmgr once in Mint. Each manufacturer does UEFI differently unfortunately.

You need to boot in UEFI mode if your windows is uefi. Do an online search for 'dual boot ubuntu and windows 10 and that should get you to the Ubuntu site which explains all the details. Ubuntu 15.10 has not been supported since July, no updates and no new software so use either 14.04 or 16.04.

Every manufacturers UEFI is different
 

Very true. Mine conveniently provides a screen shot function so I am attaching image of config screen as I had them set. At least I hope this system has attached it. In another screen I had Legacy Mode (CSM) enabled. I tried removing Windows Boot Manager from the boot options. Then the system did not boot; it went straight back into UEFI BIOS Utility. Is Windows booting in Legacy mode? I disabled CSM and the system booted straight into Windows again. Going into UEFI again I see than Windows Boot Manager is the only available option for boot priority. Something else I noticed that may mean something: while installing Mint 18 the partition manager did not identify any partition as EFI but running GParted from LiveDisk /dev/sda2 is identified as UEFI.

I forget details easily. It's Mint 18 I'm trying to install. That's based on Ubuntu 16.04 isn't it?

Based on the comments in your last post, I would guess that you had windows 10 installed UEFI which is the default and you then installed Mint in Legacy mode. The results you are seeing are what one would expect in that case. Check the Ubuntu site below which I referred to yesterday and suggested you look at. Mint uses the same installer as Ubuntu so the biggest difference you are likely to see is the background color.

https://help.ubuntu.com/community/UEFI

In my experience Mint will find the UEFI firmware and install appropriately. Boot up that USB and install (if necessary) and run efibootmgr from a terminal (as root/sudo, no parameters needed) then post the output.

Solved: Dual boot Windows 10 - Mint
 

I'm not sure where I made a mistake the first time but with your coaching the second installation was successful.

• I downloaded a new .iso image to boot
• Before booting the disk I went through UEFI BIOS Utility Boot configuration and made sure every boot mode reference chose UEFI as first or only choice
• Running from the disk efibootmgr gave reassuring output

BootCurrent: 0004
Timeout: 1 seconds
BootOrder: 0004,0003
Boot0003* Windows Boot Manager
Boot0004* UEFI: HL-DT-ST BDDVDRW CH30N

• Remembered to enable a network connection before starting Mint installer
• Installer informed me it needed to disable Secure Boot to install third party drivers, asked to specify a security key. I've booted a couple of times since installation and have never been prompted to provide that security key. More study needed here.
• This time installer recognized /dev/sda2 as efi partition, which it did not do on first installation.

Now I get the boot time menu to choose Mint or Windows Boot Manager as desired.
Thank you all for your attention and suggestions.