@JSI
You can only boot in UEFI mode off an NVMe SSD and the NVMe SSD has to use the GUIMode Partition Table (GPT). This is valid for all Windows Operating Systems.
This means, that no NVMe Controller is in-use by the OS. I wonder how you are able to boot off the NVMe SSD while running Win10.
Please check the driver version, which the listed “Intel Chipset SATA RAID Controller” is using.
Which Options do you see within the “Advanced” BIOS options regarding the on-board Intel SATA Controller(s)?
It worked for all other Win7 users, who tried to get Win7 installed onto an NVMe SSD.
Tip:
Use the Win7 ISO file, where you had integrated the MS Hotfixes into both WIM files, but follow my advices given within the chapter “B. Best/safest procedure to get Win10/11 properly installed onto an NVMe SSD”, which you can find within the start post of >this< thread. The method should work with Win7 as well.
By the way - besides the MS NVMe Hotfixes only the generic Phison NVMe driver v1.5.0.0 supports Win7 from scratch.