Go to This PC
Option #1: use the WINDOWS+E shortcut...
Option #2: click on the Documents button on the taskbar, then click on Computer on the left navigation list.
Right-click on the drive with your student number and "Rename".
When everything is highlighted, you can replace it by just by typing; you don't have to delete it first.
Once you've typed in your first name and hit Enter, you'll see Z: now.