Dell OptiPlex 7440 AIO - Will not install Windows 7 Professional

Hi,

We ordered and received 4 new OptiPlex 7440 AIO All-in-One computers without Windows installed - only Ubantu is installed.  The desktops do not have a built-in optical drive.  I get the following error message when I try to install Windows 7: "A required CD\DVD drive device driver is missing.”  I tried using an external optical drive and USB boot device to install.  I am also plugged into the USB 2.0 ports and not the USB 3.0.  I tried many of the suggestions Google has provided me, but none of them are working.  I'd appreciate any help.

FYI, I called Dell Support twice about this issue.  The first technician hung up on me when he realized he didn't know what to do to help and the second technician said I had to pay $89 for help.  When I asked to speak to her supervisor, she hung up on me. Since Dell likes to rudely hang up on their loyal customers, I'm hoping the community will be more helpful.