The HP T5515 has a standard PC BIOS - hit F10 on power-up to get into the BIOS setup screen.
Mine was password protected but that is easily sorted - just remove the backup battery for a couple of minutes!
The boot options are:
With the USB option set it booted Linux distributions from a Pen Drive and a CDROM.
The T5515 runs Linux. Mine was setup for particular environment with password logons. I didn't bother to explore this - but such lock-outs can be easily addressed by reloading the factory firmware.
Pressing and holding F3 during the boot process will get you a full screen X-Terminal with a logon prompt. I found root/root had me logged in as root.
Any comments? email me. Last update September 2011