Uninstall external drive

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I am in the process of connecting and installing a new external drive. After
it booted up and I was starting the registration (there is no external
software, it has its own built in) I realize I had made an error in the
first part. The pc shows it has been installed.
Is there any way to go back and uninstall it, correct the mistake, and start
all over again.?? There is no packaged install disk, it comes with the
"backup" procedures already installed on the drive.
Also, I have another external drive that I would like to format and start to
wipe clean and using it as empty. How can I reformat it ?, and, once done,
will the pc detect it as "plug and play" ??

Thanks

 

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The external drive does NOT appear in the Computer Management -- Storage --
Disk Management ...