Dual Booting GRUB Loader Issues

I have 3 drives on my computer;

Drive A: 225 GB SSD
Drive B: 2 TB HDD
Drive C: 1 TB HDD

Now;

Dirve A has Windows 7 installed in it - and pictures and such.
Drive B is a storage drive - videos, my steam library etc.
Drive C has Kali Linux installed on it.

IF I recall correctly; I set the GRUB loader to be installed on Drive C. I was installing in UEFI mode, but when I came to the GRUB stage, I exited UEFI mode due to the installer recommending I do this.
When I start my computer, my bios flashes like normal, then I am brought to a selection screen that asks me what I want to do, my options are along the lines of;

Kali Linux (Launch)
Advanced Options
Some Repair tool that prints an error as soon as I run it.

Launching into Kali, I can see my other two drives and access the files on BOTH drives meaning that the files are still there. I can see my windows files also on drive A.
Anyone have an idea of whats going on here? Please let me know ASAP.

If you have exited UEFI mode then in which mode you are booting your other OS? Legacy BIOS?

Show the screenshot of that error. You have given very less details about what is happening.