Inserting the SSD in slot 2 or 6 (depending on the space) is the most appropriate solution. Getting the Samsung_M2_DXE from ASRock Z77 Extreme4 -> "Beta section" is now a better test solution, as it is closer to your board's generation and hopefully with all the needed patches for current Samsung M.2 devices. Please remember that this is a driver provided by ASRock for OEM devices, it might not run in every board. Using PcieSataController is definitely a good candidate, as MSI wrote in their changelogs when supporting XP941: Add PcieSataController module; Update SataExpress module; Update AHCI module. The problem is that PcieSataController is part of Aptio V sources, while your board is using Aptio 4. The SataExpress module is not present in Asus boards, the AHCI module can't be replaced. I suggest you first try with Samsung_M2_DXE from ASRock Z77 Extreme4 -> P2.90M version. Then, if you feel lucky and have no regrets in risking your board, you can try to insert PcieSataController from a newer Rampage board.

I've ignored the error message while windows 7 installation and hit next and the installation from the USB-Stick went successfully.
But Bios still doesn't see the SM951.

I also tried flashing my bios with the module of the P2.90M version as lordkag suggested. But still no difference... :-(

No unfortunately not. I've got the OS installed onto it, then the system restarted and still didn't find the SM951.

yes.

In Windows it's called "Datenträger 0" now and it looks like this:


100MB are an EFI Partition and the rest is NTFS

Looks fine but it's not available in boot menu...

Indeed I have unplugged all other disks before the installation.
I just have plugged them in for now thereby i can write with you.

only one time.

i just tried it one more time: same thing... i can install it, when the installation is complete it counts down from 10 and restarts automatic. just before the countdown was over i unplugged the usb-stick.
then it restarts, but right after bios it stocks and says that it can't find a disk to boot and that i have to change my bios settings.

another crazy thing is that if i disable csm completely (instead of setting it to just UEFI) the windows installation program stops on the "Starting Windows"-page.
and the installation only works when i have the usb-stick connected to an usb2 port. everytime i plug it into an usb3 port there is a message that the drivers for the installation can't be found.