I'm trying to quickly set up a new XPS 8900 for a neighbor who needs to wrap it up. The system came with licenses for both W7 and W10. The family wants W10.
The system boots to W7 and does not give a choice. I opened the W10 disc expecting to boot from it to start an installation, but I notice the disc states "Already installed on your computer".
1. How do I get the computer to boot to W10?
2. Does the restore partition contain both W7 and W10 if they in the future need to use it?
You have an XPS 8900 shipped with a Windows 10 Pro OEM license but with Windows 7 Pro OEM preinstalled and likely a Windows 7 Pro OEM Factory Recovery Partition.
To clean install Windows 10, you are best to download a .iso from Microsoft (probably a later build than the DVD you have), make a Bootable USB and clean install (after Enabling a UEFI Boot with Secure Boot). See here for details: