How to delete photos from Nikon d7000?

I have a nikon d7000 and i deleted the photos from the memory card via the computer.however, although the photos are deleted on the camera, there still isn't more space on it. Does anyone know why this is and how i can fix it?

Put the card into the camera and use the controls on the camera to format the card. The software in the camera knows how it likes to see the card.

You do need to re format the sd card, did you enable the card to have the photo's read and written to.
so often we forget to move the tag on the card to transfer the photo's off the card.