Keybd and Mouse turn off during PXE boot and don't come back

[Vague Assumption]

If this is the wrong forum, please redirect this question.

It concerns HP500-400z desktops.

They function as they should, except for one major problem:  as soon as I boot them into PXE mode, the mouse and key board (USB) shut off as soon as the Win7 PXE logo appears.

A consultation with our hardware people resulted in the advice that the keyboard is bad, but I was able to get it to work under Win7 PXE mode.

In fact, I have twice gotten the keyboard and mouse to work under Win7 in PXE mode; I'm looking at it now.   But it seemed to be a sequence of undocumented steps in some magic order.

I verified that the USB ports can be all shut down from within the BIOS -- and recovered from that with F10 at the BIOS screen.

Is there any experienc with this:  it seemed to be a firmware issue in Dell systems, but these ain't Dells ;-)

I have 'cleared the keys' in the 'secure boot section of the BIOS'  Doesn't seem to help.

[Vague Assumption]

Solution:  when booting unde Win 7 PXE, as soon as the PXE OS loads, it turns off all the USB ports EXCEPT the lower two in the rear of the machine.

[Jimmy Vance]

Are the ones that work USB 2.0 and the ones not USB 3.0? Many machines need an OS driver before USB 3.0 ports will function

[Dennis Handly]

This is the wrong company for printers and PC products. You need to register in the HP Inc. Support Forum:
http://h30434.www3.hp.com/