On many HPs (including this one) the secret is Ctrl-A at some point or on some screen. I'm not sure exactly when you need it hit it, but once your'e in the BIOS, just hit ctrl-A, go to System Info, hit ctrl-A, keep going. Then go into System IDs and the option will be unlocked. If it's not, you didn't hit ctrl-A in the right place (may need to do it during start up, like I said, I'm not sure exactly when on this model, but I've done it using this method before).