Also "Installed" included all Devices whether Physical or Virtual so Window7 system with a Windows 7 Virtual machine would need two licences as to use the VM you needed the licence for the Host and a licence for the hosted OS
Generally speaking, if you can disable Secure boot on BIOS, you can install. It doesn't mean it will be an easy task.
Before you begin, make the Factory recover disks (launch from BIOS). If it fails to install Win 7 you can restore win 10.
Can you give us the brand and model of the new laptop?

thanks ...
Laptop is a Jumper EZBook 3 Pro from China, it has Win 10 pre-installed on an eMMC drive but there's also an empty M.2 slot. I will research the drivers, maybe install Win 7 onto an M.2 SSD, if it boots and everything works, I'm happy. If it doesn't the Win 10 eMMC drive is untouched. Either way I'm not too worried, this is my first laptop, I wanted something cheap and cheerful, worst case scenario is I'm stuck on Win 10, (or Linux, which does work with this laptop).
Be careful when you choose the M.2 drive. Some of them use the PCIe Gen 3 others don't.