Hi TheLEGObrick
I am Dave, an Independent Advisor, I will help you with this, please note, this process will delete all data on that drive
Click your Start Button, then just type cmd
On the resulting list, right click Command Prompt and select 'Run as Administrator'
Run this command and hit Enter:
diskpart
Run this command and hit Enter:
list disk
(Make note of the disk number you want to convert and enter it into the next command - replace X)
Run this command and hit Enter:
select disk C
Run this command and hit Enter:
clean
Then close Command Prompt
Go back into Disk Management and that whole drive should now be unallocated space, which you can right click and select 'New - Simple Volume' on . . .