The only way the registry hack would ever work is if the hardware switch was wired into an I/O logic gate, lol.
Take that beast apart and check for loose wires at the switch and at the header on the board. If it turns out to be the switch, you could always short the pins that leave the wireless adapter on, and just disable it via Windows' wireless manager, though I'm not sure if there will be a detriment on your battery life. Also, a thought would be to find another mini PCI-e WLAN card and perform a swap, to see if the issue still persists. Most HP laptops allow you to access the wireless card through just one small panel, so you don't have to tear the entire machine apart if you're not comfortable.