it has become Unallocated Space now. Do the following and create a new partition:
Step 1
Click the "Start" button, right-click "Computer" and choose "Manage."
Step 2
Click "Disk Management" from the left pane of the Computer Management window to access drive management tools.
Step 3
Right-click "Unallocated Space" from the graphical hard drive display and select "New Simple Volume."
Step 4
Click "Next" three times until you get to the formatting screen. By default, NTFS is selected. Click "Next" to allocate the space to a new partition and format it.