I have a windows 7 pc, and I had installed windows 8 on an SSD, so it was the only partition on that SSD. I've now realised that I never use it, so I went to uninstall it and followed these steps.

The PC now boots into 7, as expected, however I can't delete or format the drive that has windows 8 on it. The format dropdown selection is greyed out, and I tried to just simply delete all of the files and use the disk as is, but as windows 8 isn't there, I no longer have rights to delete all of the files, apparently. The drive in question has 3 partitions, one that I made for the win8 system, and 2 smaller system-created partitions (one 300MB recovery and 1 100MB EFI)

How do I go about formatting the drive?