So I am selling my macbook and I reformatted the hard drive using the disk utility on the OSX install disk. I zeroed out the hard drive as well to protect all my data. However when it was done, the disk disappeared and I couldn't install the OS! It's like the hard drive doesn't even exist. I put the computer into firewire mode and plugged it into another computer and it only mounted the DVD drive. What the hell do I do to install the OS on the HD? Help me please!