I have a rMBP with 512GB. Half is running windows 8.1 the other half Mavericks. After some problems with the windows partition I decided to delete it. I didn't use the bootcamp remove option. However the partition still exits, not only is it taking up space from my internal hard drive but I can't access it now. I had previously backup everything. I have tried to format/erase the whole hard drive but every time I do I get the message "disk Erase failed with the error: couldn't unmount disk". Now after pressing the power button and the alt option key I see the windows partition and the recovery hd. I don't know what to do. I would appreciate any help.