The HP t5125 has a standard PC BIOS - hit F10 on power-up to get into the BIOS setup screen.
The boot options are:
With the USB option set it booted Linux distributions from a Pen Drive and a CDROM.
The t5125 runs Linux (kernel version 2.4.25). If you right-click on the desktop you can open up a console which will let you poke around. If you wish to logon as root the password is "root"