I just got a mac pro 15 inch and I started it with my time machine from my previous computer, but once i got the computer backed up with the time machine i decided to erase everything to start fresh, so I reset the computer and pressed cmd+r and i think i erased everything except of where it says Macintosh HD, disk 1 and os X base System. So now there it shows a window saying there is no disk where to install mac os x ( the partition tab on disk utility its all grayed out) please help!