WinPE4 and HP Elitedesk 800 G1 issue

We are trying to boot a HP Elitedesk 800 G1 into WinPE and we get as far as the 'Restarting DHCP Client Service' message.  I have added the Windows 7 & 8 drivers into the PreBoot Driver Database and can see from the BDC folder that its there on the main NS and has replicated to the site servers.  Can anyone shed light on why this is not working??

Thanks