Disk Utility won't allow "erase" on my HD

[Loonytik]

I'm selling my Macbook Air and want to erase the hard drive completely and reinstall the OS. When I go to the disk utility and select the Macintosh HD the only option I am given is "Erase Free Space". The security options and "erase" are greyed out.

What's going on here? How can I erase the full volume?

Thanks!

 

[Ccrew]

Won't allow you unless you're booting from install media.. ie: DVD. Otherwise you're trying to delete the disc the utility is running from.

 

[Loonytik]

I'm using a Macbook Air late 2010 with the software install drive. The only options are to reinstall OSX or run a hardware test. How can I get it to boot from there so I can erase the original OS?

 

[Ccrew]

I don't have an air, but in a regular install when it gets to the first screen after the language screen on a re-install it enables the menu, and under Utilities is Disc Utility. You run from there.

 

[Loonytik]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)

Perfect. Thanks