Type "Cmd" into the search box on left end of command bar and click on "Run as Administrator"
Type "Diskpart" at the command prompt. Spend a little time with Help to gain a basic understanding of the commands. Typing a wrong command can lead to complete loss of system partitions!
Enter "list disk" to determine the disk number of the disk of interest. Probably will be disk 1.
Enter "select disk N" where N is the number of the disk of interest.
Enter "detail disk" to help confirm the proper disk is selected.
If things work this far, let me know and more commands to follow. Diskpart is a dangerous utility so be careful!