@ sl@sh
I recently did a Windows 7 x64 UEFI install on my system. Reading most of the guides online suggested disable CSM and I got same message as yourself. I even tried some other things in threads I read and none worked.
How I finally got things going was by having CSM enabled and option
Boot from Storage Devices [Legacy OPROM first] to
[UEFI driver first].
During installation I formatted the SSD via SHIFT+F10 to open command prompt and used DISKPART.
DISKPART
LIST DISK
SEL DISK # (replace # with hard disk you're certain is target drive)
CLEAN
CONVERT GPT
EXIT
Then closed command prompt and continued with install by selecting the unallocated partition on SSD (I did no setup of partition by installer and let it allocate space automatically).
Later once I reconnected my other HDDs to system I'd get a delay in boot up, I noted a flashing cursor on screen straight after ROG boot up logo. SO I changed option
Boot Devices Control [UEFI and Legacy OPROM] to [UEFI only] , I may have been getting a delay as my HDDs are MBR and not GPT at present and perhaps UEFI was searching to see if those had any OS, etc.
My UEFI defaults have Secure Boot / Fast Boot / CSM enabled, so just to recap from UEFI defaults I changed only:-
Boot Devices Control [UEFI and Legacy OPROM] to [UEFI only]Boot from Storage Devices [Legacy OPROM first] to
[UEFI driver first]More info regarding my experience with getting Win7 x64 UEFI installed in this
thread, yet to update it with last UEFI option change (Boot Device Control).
I have an Asus Maximus VII Ranger not VIII Ranger but only sharing this info as perhaps it may help you.
