if it is not responding to any method, maybe he sold you a netbook with a broken hard drive ?
as a last resort you can try:
dd if=/dev/zero of=/dev/sdx bs=16m
this should destroy the drive so it could be rebuilt by gparted
(or a linux or windows installer).
edit: this mite be all that is necessary:
dd if=/dev/zero of=/dev/sdx bs=512 count=1