Couldn't Unmount Disk in Yosemite
I am trying to erase my MacBook Pro to be like new, so I hit "command-R" upon startup and tried to erase using Disk Utility. The error "Couldn't Unmount Disk" pops up when I try this, so please let me know what I am doing wrong. Thank you!
MacBook Pro, OS X Yosemite (10.10.3), null
