can't get started

[Impavidus]

If Windows 10 has been installed in UEFI mode, boot the Ubuntu live disk (usb or dvd) in UEFI mode too, which will install Ubuntu in UEFI mode. If Windows 10 has been installed in legacy mode (unlikely), stick to legacy mode.

Use Windows tools to shrink the Windows partitions, so you get enough unallocated space on the hard drive to install Ubuntu. Make sure Windows uses basic partitions, not dynamic partition, or you'll have a problem later.

How have you created the live disk? Don't burn the .iso as a file to the dvd, but burn it as an image. When using a usb, don't copy the .iso into the usb's file system like you do with ordinary files, but "burn" it to the usb drive itself, so that the .iso becomes the usb's filesystem. You need special tools for that, like mkusb or rufus. With some of these tools, you have to specify whether you want to boot it in UEFI or legacy mode. If you choose the wrong option, it won't boot. Most people nowadays use usb. Many computers no longer have a dvd drive. Maybe that all sounds obvious to you, but plenty of new users get this wrong.

You can set usb or dvd before the hard drive in your boot order, or use the boot once option. Some computers don't boot from every usb port. Trying a different port may help.

I read that this computer may come with nvidia graphics. Once it starts booting, you may have to set the nomodeset boot option in the live session, or you may get a black screen. Once Ubuntu has been installed, you can install the proprietary graphics driver.

You didn't mention the release of Ubuntu you attempt to install. 20.04 LTS would be best for a new user.

[oldfred]

Do not turn Legacy on, if Windows is UEFI which it should be.

Dell typically needs UEFI update, if SSD also SSD firmware update.
It needs UEFI setting for drives changed to AHCI, not Intel RST nor RAID. But if dual booting with Windows you must first install AHCI drivers into Windows or it will not boot.
Often better to have UEFI Secure boot off. And UEFI fast boot off, as that assumes no system changes & you are changing system.
Newer systems need legacy off to boot in UEFI mode.
And in Windows you need Windows fast start up off as that sets hibernation flag and then Linux NTFS driver cannot see the NTFS partitions. Note that Windows updates may turn fast start up back on.

Shows live installer with screen shots. Both BIOS purple accessibility screen & UEFI black grub menu screen 20.10 uses grub for both
https://help.ubuntu.com/community/UEFI
Shows Windows screens
https://askubuntu.com/questions/2218...s-10-with-uefi

[dave_moran]

the above mentioned Dell link seems to be telling me that Ubuntu won't work on my XPS8700

when i use the F12 key, it takes me to my BIOS set up.

i have never seen the Boot Once menu.

[oldfred]

Is this an older system? Sometimes vendors reuse model number.

This is old thread as mentions 12.10, but issues should be similar.
Dell XPS 8700 with Intel SRT - Install 13.10 - just change UEFI to AHCI mode
http://ubuntuforums.org/showthread.php?t=2199382