You will need to do a hard reset if you don't the username and password, it's the only way to bypass it really, unless you hire an advanced hacker.
Jack.
The problem is likely to be within the headset itself, if not the drivers or connection, did it come with any warranty?
I always buy my gaming head sets from Turtle Beach, never had a problem.
Jack.
I didn't have a boot via USB on my BIOS when I wanted to boot from my external hardrive although it was detected as a normal hardrive and had to select the USB hardrive over the SATA within the BIOS.
Jack.
I wouldn't be surprised if this was possible for obvious reasons, but as you suggest with todays technology the computer would more than likely shut down as manufactures need to take into consideration hazards such as the fan suddenly stop working etc.
Just my opinion.
Jack.
You should really be getting some kind of beep but I would wait until you have the RAM first as the RAM might not be the main problem, could be power.
Jack.