I was using Windows on the machine before all this started happening , so I think , the rest of the partition is either unallocated memory or whatever kind of partition windows uses for its thing.

I dont know much about BIOS , but you are asking is it grub or a master boot record right? I haven't a clue to be honest, I've been doing some retard-grade tinkering with different operating systems , and I think it's moved between grub and a master boot record . I don't know , maybe you could instruct me on that ?

I don't know what Bitlocker is , but if I was to hazard a guess , I would say that it is not in play .

UEFI is enabled .