Have you made sure you're not running "fast boot" or whatever it is called then gone into BIOS and changed the boot order to boot the DVD first? I think Ubuntu should boot in UEFI mode but if it doesn't you'll need to enable legacy mode also (don't recall what it's called, sorry).

i could not find any definite info on "ASUS A/F/K20" - however, if it's a new machine, it's likely to be an EFI thing.
plus, don't be surprised if additional setup is required.
linux always takes a while to catch up with new hardware.

The two setting I found were "UEFI" and "Safe Boot". Either of them could prevent a different OS from installing, one (UEFI I think) stopped live-cd images from even loading, both together really messed things up royally.

The "UEFI" alone would not stop current Ubuntu from loading (they licensed a certificate from MS) so I am betting you have more than one setting to change.

Note that changing these settings MAY, but may not, disable to current installed OS.
I have had results both ways, and have not been able to track down what makes the difference.
(generally, changing the setting back restored the original conditions)

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Good call there on "Safe Boot", I forgot that I have that turned off on this triple-boot* ASUS laptop. With it on it will only boot the Windows 10 UEFI partition.

*Debian, Slackware and Windows 10 (listed by frequency booted).

Hi Guys, thanks for all the replies, I have tried a bunch of things in the bios which by the way seems to have changed a fair bit from earlier computers. What I did discover however is: In order to install any Linux system or run live on a W-10 computer you have to download a thing called "Oracle Virtualbox". It is a real pain to work with and I am totally P.O'd with Microcrap. It seems they are doing their best to prevent you from using or installing any other software than their own which I have no use for. Also, once you do manage to install Linux through VB, you are actually running inside Windows as opposed to running Linux by it's self. The result is a distorted desktop and less control over options and pref's.
So far I have not found a way to uninstall Microslush but if I do I will post my findings. Thanks again to all the replies.Happy New Year, Tukatz

Using VirtualBox can be a good idea. However, that is not the same as dual boot.
BIOS changes aren't that much of a worry just turn off "Secure Boot" if you want to boot an Ubuntu disc and consider turning on "CMS" (or whatever the heck it's called) to emulate old BIOS so that you can install Linux.
If you want to get rid of Windows then you just install Linux on the who;e hard disk drive and removed Windows entirely. Much as I love Linux I would not suggest removing Windows for many reasons and I even keep it around myself if for no other reason than for warranty purposes.

HOLY MOLEY! Thank you, Thank you, Thank you! I finally found "Secure Boot" & the "CMS" . It works!! It was well hidden and since I was used to the older BIOS system it was not easy to find, a lot of poking around but it finally paid off.
If I really need Microslush (highly unlikely) I can always use my wife's computer which is running an up-dated W-10 Vsn.
She won't switch to Linux, won't even try it. I trashed MS 10 years agoi and have no intention of reverting so a BIG thanks to all who have helped! Cheers, Tukatz

Glad to hear it's working out for you.
You should mark the thread as solved using the link near the top of the page. I tend to recommend keeping Windows around as I~ know that there are some things which cannot be done under Linux so, sadly, Windows can be required when one least expects it.