I have a MacBook that I am getting ready to sell. It has two partitions on it, the Mac OS X 10.7 one and a Boot Camp one. I am trying to repartition the HD so that it only has a Mac OS X partition on which I will reinstall Lion. When I boot to the Recovery HD and try to do this in Disk Utility, I get the error "Partition failed with the error: Couldn't unmount disk." I can no longer boot to the Mac OS X partition as I've already erased it. I've tried using the OS X Recovery Disk Assistant (http://support.apple.com/kb/DL1433), but because I created the bootable USB on my MBP running Mountain Lion, I believe it made a Recovery Disk only for ML and I can't not boot my MacBook from it. Any ideas? Any help is appreciated. Thanks!