I haven't used VirtualBox in years, but did this machine have a disk before, and it just stopped working when you added the new controller? Did you attach a disk to the controller? Is there a boot-order option where you need to tell it to use said disk?
#VM on virtual box won’t boot after adding controller SATA
inner fox
inner fox
Windows is your host OS? This is likely the wrong place for help then. I don't have any assistance I can give on that. If the machine isn't booting because it can't access the disk, that's an issue on the host, and if the host is Windows.....
inner fox
The file you can't read is in c:\whatever, you're having a windows problem right now