I recently decided to double boot Windows and Kali Linux, but when I install Kali Linux and then try to boot into it, I only get to the GNU Grub command line. I've tried various commands to get out of it, loaded the kernel and exited, but then it just threw me into Busybox (initramfs), at which time I lost hope. When I tried to exit it, it just crapped out and froze. I've tried reinstalling it multiple times, but it always says the same thing.
Do you know how I can fix this?
You should start with a set root=(hd0,msdos1) on a grub prompt. Or something like this depending of your configuration. Note that you can be helped with the TAB key which indicate how the command can be legaly completed. Type set root=(hd0, then TAB for example. It will show you the different available partitions).
Once the root of grub is set, something like linux /vmlinuz root=/dev/sda1 ro then initrd /initrd.img then boot start the whole thing.
This has been tested on a Debian with a unique file system. Then, the actual filenames may vary, but can easily be discovered with the TAB key. If you want us to help you, you should indicate what the (hd0, TAB does show. You should also type linux / + TAB and tell us what is printed.
Here /dev/sda1 is the first partition of sda. It may be inadequate (if you have created separated / and /boot for example or if Windows is in the first partition). You could type ls (hd0,msdos1)/ and also with other partition (msdos2...) to have the different partition contents.
root=parameter in the kernel command line?