Currently Being ModeratedMay 4, 2012 10:05 PM (in response to miguerrolas)
Boot from the install media (Recovery Mode in Lion, Install DVD all others), do a full reinstall with the Erase & Install mode. If unsure this is happening, run Disk Utility from the install media and erase the Macintosh HD volume prior to doing a full reinstall. When it finishes and is about to reboot, shut it down instead. That way, the new owner will be able to set it up like new thanks to Setup Assistant.
Currently Being ModeratedMay 5, 2012 1:38 AM (in response to miguerrolas)
Depending upon the level of security you may choose to erase the hard drive using various levels of security. The more secure the longer the erase procedure takes. Then follow the advice above.
Currently Being ModeratedMay 5, 2012 4:47 AM (in response to miguerrolas)
Thanks guys but I just notice that I don't have my back Disks, am I screwed?
Currently Being ModeratedMay 5, 2012 5:35 AM (in response to miguerrolas)
Apple can send you new installation disks for a fee. Have a credit card handy and the serial number of your MBP when you give them a call. (This assumes that your MBP is 2010 or older.)
Currently Being ModeratedMay 5, 2012 8:53 AM (in response to miguerrolas)
If the Mac has 10.7 Lion, you don't need or will have physical install media. But I'm guessing that is not the case.
While you procure a new media set, as per Ogelthorpe's indications, you can and should do one last backup of the drive. Best would be a bootable clone onto an external drive. Do a Get Info of your boot drive to determine exactly how much space is being used. Then use the Mac's Disk Utility to create a partition of that size onto an external drive. Finally, clone the drive onto the newly created partition: can use Disk Utility, just Restore onto the partition, or use Carbon Copy Cloner or Super Duper, both are free for this operation.
You can then boot from the external drive (hold down Option before the startup chime) and use the external's Disk Utility to erase the internal drive.