Format that big partition you made earlier and copy all files from the Windows 7 drive onto it.
Shut down and install the SSD that has Windows 7 on it.Go through with the Windows 8 installation and boot from Windows 8.You should also see the UEFI partition and system-restore partition at this point.Now, create a second partition with the 100 GB, which will be used as an installation target for Windows 8. This big partition will be where Windows 7 will end up. Create one big partition spanning the whole drive, minus 100 GB.Boot off the Windows 8 install USB stick.Put that disk away for the moment and have the NVMe SSD as nothing more than a storage device. Install Windows 7 on a separate HDD/SSD, boot into it and install the Intel NVMe driver.You basically want the Windows 8 bootmanager and UEFI loader partition on the drive, which then loads the Windows 7 EFI kernel loader. I spent a couple days with this problem and figured out a complicated fix, but it does work. So.looks as though Windows 7 users are out of luck? Not exactly.
I will paste here in case something happened to the original:
