Many older computers have issues booting from external USB drives, and booting from CDs is usually slow and prone to errors in modern operating systems.
Here's how to boot from an USB drive despite of how old the computer is:
- In the BIOS, disable Legacy USB Storage.
- In the BIOS, enable CD as first boot device.
- Download and burn in a CD the Plop Boot Manager.
- Write your favourite operating system into an USB drive.
- With the CD in the CD reader tray and the USB drive plugged in, reboot .
- In the screen that will appear, choose "USB".
- If that doesn't work, with USB selected in the menu, press shift + enter.