I have a MacBook Pro (13-inch, late 2011) running Mac OS 10.10. My hard drive crashed and I was not able to repair it using Disk Utility. I replaced the hard drive and installed from my Time Machine back up external drive. This seems to have fixed the problem. My question now is, how to I completely erase the old (broken) hard drive? I want to wipe it completely clean to get rid of all information on it. When I use a USB adapter to connect it to me MacBook Pro, I can access the files, but I can not erase the disk with Disk Utility. Any suggestions?