Hello,
I am new to Kali. The trouble started upon installation when as I was installing GRUB Boot Loader it said something to the effect of : "As there is no other OS in this machine...etc..." but I was thinking "There is another OS in this machine, just in a separate partition". What the UI wanted to know was whether or not to install GRUB on the primary drive. I did some quick googling to that effect and it seemed like the best thing was to always install on the primary drive so I clicked "Yes". Then there was another screen with a question of which drive (maybe something else? I can't quite remember, unfortunately) I wanted to install GRUB and I remember I picked the first one listed in the menu. If I had to bet this was where I made a mistake since I didn't really know what I was being asked.

Predictably, Windows Boot Manager is not in the GRUB Boot Menu. If I go in my BIOS menu and go in boot options "Windows Boot Manager" is in there and works fine. In my attempts to fix this I came upon some recommendations and what I found was that I should run os-prober. I did run it and I got a "cannot find a GRUB drive for /dev/sda1. Check your device.map" error, although in my case I'm pretty sure it was sdb1 instead. I also saw the advice that I edit the grub file to write or uncomment "GRUB_DISABLE_OS_PROBER=false" in /etc/default/grub, which I did (uncomment) before you suggest it. I don't know if that's what caused this further change but whereas before os-prober returned me that error, now it returns me nothing, just an empty line and then the prompt again.

I assume the return from "fdisk -l" would be useful so here it is:

Disk /dev/sda: 1.82 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: TOSHIBA DT01ACA2
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xd3590ccb

Device Boot Start End Sectors SizeIdType
/dev/sda1 * 1026048 3907024895 3905998848 1.8T 7 HPFS/NTFS/exFAT


Disk /dev/sdb: 447.13 GiB, 480103981056 bytes, 937703088 sectors
Disk model: TOSHIBA-TR150
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 0D91E19E-5110-4AEB-AB97-33849F7ECFEB

Device Start End Sectors SizeType
/dev/sdb1 2048 206847 204800 100M EFI System
/dev/sdb2 206848 239615 32768 16M Microsoft reserved
/dev/sdb3 239616 479931529 479691914 228.7G Microsoft basic data
/dev/sdb4 936636416 937699327 1062912 519M Windows recovery environment
/dev/sdb5 479932416 479934463 2048 1M BIOS boot
/dev/sdb6 479934464 934635519 454701056 216.8G Linux filesystem
/dev/sdb7 934635520 936636415 2000896 977M Linux swap

Partition table entries are not in disk order.


Disk /dev/sdc: 698.64 GiB, 750156374016 bytes, 1465149168 sectors
Disk model: 2115
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x000b1c3c

Device BootStart End Sectors SizeIdType
/dev/sdc1 63 1465147391 1465147329 698.6G 7 HPFS/NTFS/exFAT


Disk /dev/sdd: 3.73 GiB, 4002910208 bytes, 7818184 sectors
Disk model: DT 101 II
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x2052474d

Device Boot Start End Sectors SizeIdType
/dev/sdd1 6579571 1924427647 1917848077 914.5G 70 DiskSecure Multi-Boot
/dev/sdd2 1953251627 3771827541 1818575915 867.2G 43 unknown
/dev/sdd3 225735265 225735274 10 5K 72 unknown
/dev/sdd4 2642411520 2642463409 51890 25.3M 0 Empty

Partition table entries are not in disk order.
I have some live bootable live versions of an OS ready to go, if that's useful.

Any help appreciated.