Before you click "Format," you must choose a . This determines how data is organized and which devices can read the drive.

and click on This PC in the left sidebar.

Now go forth. Wipe that slate clean.

Side note: Disk Management looks intimidating. It’s just a map of your storage. Don’t touch the drive labeled “C:” unless you enjoy reinstalling Windows.

Close File Explorer. Eject the drive physically, plug it back in, and try again. A virus scanner might be pawing through it.