After you have used your USB to try or install Endless, you can reformat it so that you can reuse it. Here are instructions on how to do so.
If you are using Endless or another Linux system with the GNOME desktop:
- Search for "Disks" on the desktop and start the Disks utility.
- Find your USB disk on the left, and then at the top right, click the ☰ menu icon, then select "Format".
- The defaults ("Don't overwrite existing data (Quick)" and "Compatible with all systems and devices (DOS/MBR)") are OK, so hit "Format".
- Then hit the + icon to create a partition for your data. It will default to creating one partition which takes the whole disk, so just choose "Don't overwrite existing data (Quick)" and then "Compatible with all systems and devices (FAT)" and hit "Create".
If you are using Windows:
- Download a tool such as Rufus from https://rufus.akeo.ie/ which allows you to format USB disks.
- Run it and select your USB drive. Leave Partition scheme as "MBR"... and File System as "FAT32" and ensure that only "Quick format" is checked, then hit "Start".