You really can delete every thing on a HD i must say it's hard to do but you can do it if you know how to.
I still remember my first Computer it was a Compact 1200 14inch screen crapy speakers,114mhz CPU,1242Kb of ram,538MB of HD,28.8Modem,and with windows 3.1 and with DOS mode.
Nice huh.I should have put a fire cracker in it and go Boom.
HA
HA
Explodeing Computer