First of all you have to find the correct update file for Z400 series. go to http://h20564.www2.hp.com/hpsc/swd/public/readIndex?sp4ts.oid=3718669
Choose the OS... Windows Pro 64 usually.then choose BIOS under the Download Index
Download the 03.57 BIOS to your desktop... (it is SP63460, about 4.5 MB) Double click on it, Next, I accept... , Next, Next, close the
window that auto-opened.
