I'd like to sell my macbook for spares or repair. it's quite old around 2005/6 (using snow leopard 10.6) and will only boot up in safe mode. I can't boot it up when trying to boot a restore dvd - (in recovery mode cmd+R) as I just get those scrambled horizontal lines (as I do when trying to boot in normal mode). I'd like to wipe it clean before selling, however I don't seem to be able to do anything with it. is there anything else I can try to reset it?