If so, and you've duplicated them for a backup copy, you can reformat that partition and use it for additional storage of personal files instead. Alternatively, you can go into Disk Management (an Administrative tool in the Control Panel), right-click the partition, select "change drive letter and paths," and then delete the drive letter. You can always add the drive letter back later if you need to access the partition, but otherwise it will prevent Windows from constantly reminding you.

Hope this helps,
John