  Its probably something to deal with the UEFI.  In the BIOS, is there any option to use both UEFI and 'Legacy' or BIOS? Or maybe when you first turn on the computer to select the USB boot option, there may be something listed as Legacy and the USB you are trying to boot from.   Sorry i should have mentioned i have also tried UEFI and Legacy options. I managed to install Windows 7 Pro x64 on the XPS 8900.   What i think was the problem is that the motherboard has a USB3 only controller.  The back plane has "USB 2" ports but i think that they actually go to a USB 3 controller which is causing the issue.  I think it may be causing some kind of limbo mode error where WindowsPE gets confused as it's not purely a USB 2 port since Windows 7 does not support USB 3 out of the box.  I had tried to load the USB 3 drivers when it asked for the drivers but it did not accept the drivers for what ever reason.    The only way i could find to install was to use a DVD version.  Going to the DVD instantly worked and i did not have to load any extra drivers during the install.   I should note that i did have to burn a CD with the extracted versions of the driver installs to get the USB ports to work properly once i was in Windows.  I could not get my mouse to work at all and i had to navigate via keyboard only.  Installing the Intel USB 3 drivers fixed the issue straight away though and i dont seem to have any issues after installing them.  I also had .Net Framework 4.6.1 and Kernel-Mode Driver Framework 1.11 installs on there aswell as some of the Intel drivers required them.  
Hey guys, We just purchased an XPS 8900 for our sign business and unfortunately we have some legacy software we have to use Windows 7 (working with obscure vinyl printers).  I cannot seem to get it to install at all.  The problem is that i get through to just before the drive selection to pick which drive to format and install Windows on, it stops and gives me this error: "A required CD/DVD drive device driver is missing. If you have a driver floppy disk, CD, DVD, or USB flash drive, please insert it now.Note: If the Windows installation media is in the CD/DVD drive, you can safely remove it for this step."This is where i am 100% stuck at.   The PC shipped with Windows 10 and bios version 2.1.0.   So far i have tried:All installs have been tried as GPT UEFI with bios set to AHCI and secure boot off and using the USB2 port on the rear for the memory stick and two seperate memory sticks have also been tried.  Bootable ISO was make with rufus 2.7 Bios 2.1.0Windows 7 Pro x64 non SP1Windows 7 Pro x64 SP1Updated bios to 2.1.3 (newest)Windows 7 Pro x64 non SP1Windows 7 Pro x64 SP1Modified (via NTlite) Windows 7 Pro x64 SP1 (to include all available x64 drivers)[URL] bios to default settingsWindows 7 Pro x64 SP1Modified (via NTlite) Windows 7 Pro x64 SP1 (to include all available x64 drivers)Install brand new 2TB WD Black Hard Drive (to avoid the windows 10 GPT install)Windows 7 Pro x64 SP1Modified (via NTlite) Windows 7 Pro x64 SP1 (to include all available x64 drivers)  What is making me pull my hair is that WinPE can SEE AND ACCESS both the CD/DVD and the existing hard drive as well as the USB 3 ports.I do not understand what driver it could possibily be asking for.  Any help would be greatly appreciated as i need to get this machine running ASAP.Thank you
XPS 8900 troubles installing Win 7 Pro