Hi there enzo11,
I would agree with thejackal85.
This shouldn't be your OS drive right?
Do you have some data stored on the drive? In case you do, you will need to use some partition/data recovery software in order to retrieve the data.
In case you don't, you can go to Disk Management, delete the existing partition and partition and format the unallocated space.
Cheers,
D_Know_WD