Im still not entirely sure how the system and storage is setup..
Is it possible to remove the drives with the important data? Then we can get down to business with the boot drive. Is the primary goal accessing the
data, or specifically getting this build up and running?
Either way, getting it down to its basic parts is nearly always a good step when dealing with some of the more vague issues that can crop up; single
stick of memory, boot drive, limited peripherals, etc.
Usually, there are a few methods to access the firmware at boot, but I believe ASRock is F2 or Del. You can essentially just mash one of them
repeatedly while its turning on until it goes into the interface. Makes it so you dont have to catch the right moment, though you may get some angry
beeps depending on your setup
Like others, my guess would be something went wonky in the efi/boot sector.
The
easiest solution to this is to reinstall the OS. However, if there is data on the boot drive that is important, that will need to be copied
elsewhere first. It will also mean setting up dual boot again, if that is desired. This may include funky stuff for strange interfaces, depending on
what it was used for before.
Essentially, my SOP for bringing a system like this "back into the fold" is to start from a fresh OS install and go from there. Thats regardless of
whether its working properly.
Before we get there, we need to make sure there is nothing on the OS drive that we need. Once its been backed up, we can go ahead and install the OS
again and if we go for the full format & install, it will also give us a fresh start on the boot sector as well.
Its kind of the nuclear option, however, in circumstances like this where its not our main system and its been sitting around for a while.. it tends
to be my go-to.