Never use the provided DVD to install Windows 10. It will be an obsolete old build of Windows 10 meaning you'll essentially need to install Windows 10 twice (clean install the old build then upgrade install the new build). Moreover the optical drive fails to pass SecureBoot. Download a Windows 10 RS1 .iso direct from Microsoft and make a Bootable USB setup  to utilise the GPT Partition for UEFI BIOS, make sure its FAT32 formatted and make sure your UEFI BIOS settings have Legacy ROMs Disabled, Legacy Boot Disabled and a UEFI Boot with SecureBoot Enabled. See here for details: [URL] 
Hi, We bought several optiplex 3040 that came with windows 7 preloaded, all the machines include a purple cd with windows 10. I follow the instructions to reboot in UEFI mode, access the CD menu and selected to restore the PC, the machine starts working and after it shows that the restore is complete it reboots and shows the same menu all over again. What do I have to do in order to install windows 10 using this CD? what am I doing wrong? Thank very much for your help Kind regards!
How to use Dell CD to install windows 10