Just bought my wife a re-furbished dell computer. It came with windows 10 UNactivated. So instead of activating windows I would like to boot linux mint from a usb stick for her to try. I have started and re-started the computer while hitting just about every "f" key to get to the boot tab. All I get is pink lines across the screen. I do not want to activate windows 10 at this time. Any thoughts?

Welcome to LinuxQuestions.

What is the model number of your Dell? I assume it boots to Windows successfully?

What ISO did you download?

How did you create the boot USB stick? The preferred method according to the Mint install guide if using Windows is using Etcher, if using linux I prefer just using the dd command.
https://linuxmint-installation-guide...test/burn.html

With the later models select F12 for the boot menu and pick the option associated with your USB flash drive. If you see a UEFI option try that. Typically there are instructions when the BIOS/UEFI splash screen is displayed that indicates which function keys to press for configuration or boot menu.

It is a Dell E5470.
It has Windowns 10 installed but NOT activated.
I did not activate windows 10 b/c I wanted my wife to try Mint before giving Microsoft any of my info.
The opening screen tells me to activate windows but I would just like to try and boot the usb drive.
I downloaded mint 20.2 from the linux website using Yumi to install it on the usb drive.
I have used mint for a couple of years and wanted my wife to try it.
Do I have to activate windows before I can get to the boot tab to select usb boot?

You should not have to activate Windows. All of my PCs are fairly old in computer time but as far as I know the BIOS/UEFI with the Dell logo should appear before you see the Windows opening screen.

You do need to tap the F12 key continuously until you see the "Preparing one time boot menu" message.

Which yumi version are you using i.e legacy or UEFI? It depends on how the laptop is configured but I would assume its UEFI. While yumi should create a bootable USB drive it isn't my tool of choice. I prefer just to use the dd command. Since you are already running Mint you should be able to right click on the ISO file in the file browser and select make bootable USB or use USB image writer from the Accessories menu.

Also make sure you have verified the downloaded ISO file is good using sha256sum
https://linuxmint.com/verify.php

Can you get to bios using the owners manual F key?

If not then maybe Windows is locking the drive. https://support.lenovo.com/mx/en/sol...e-thinkstation

Suggest to use balenaetcher to put the iso onto the usb https://www.balena.io/etcher/

I think Yumi has issues when booting in uefi mode.

Thanks to all. I got it.

Will you post your solution for others with the same problem.