The installation of grub has 2 parts: the resource files, and the boot loader.
[Concerning non UEFI boot] Each OS installation has its own resource files [located in the same partition than the OS you have installed), but the boot loader is always installed on the master boot record. Effectively, the boot loader that is installed later will overwrite the former. In that sense, you can have only one full functional grub at a time.
So, don't worry, one of your grub is not functional.
The fact that your Windows, on the non-removable disk, cannot boot with the help of the Linux removable disk, means that your boot loader has a part that is needed located in the Linux partition, as I wrote, there are 2 parts.
(...) I either have 2 grubs, which doesn't make sense, or I lose the option to boot into Ubuntu when my hdd is connected if I do the windows repair thingy.
No, you have only one that is functional. The one with the 2 parts, one has now only one part, as the Linux one rewrote your MBR.
In your case, you had first Windows installing its bootloader in the MBR of your non-removable drive, and after that, you installed a Linux distro, and you probably didn't use the option "Install Linux next to Windows" (dual boot), so the only (MBR-)bootloader that remained was the Linux one, as you didn't specify explicitly to keep the ability to boot Windows during the install.
I had problems sometimes with install that installed the MBR in the wrong partition, I think it happens.
I googled online and what I found out is that I either have to install grub on my primary drive; or use a windows recovery disc to repair the MBR.
As you have 2 disks, you can have 2 functional grub, the Windows grub in the MBR of your Windows disk, and the Linux grub in the MBR of your removable disk.
You can use a live CD/USB (everyone should have one to fix bad things that happens to boot, more often than we think).
A live CD with any distro, and an ethernet cable, and you download boot-repair,
or a boot-repair disk: To download here or here.
(For people who cannot boot from the live CD or USB, obviously, they have to change the boot order in their bios.)
You can make a bootable disk with Rufus or Unetbootin for instance.
Tutorial: https://linuxhint.com/ubuntu_boot_repair_tutorial/
There are other disks that can help you alternatively, like Hiren boot (this one is very good as you can use both Windows and Linux to repair your system, from the same ISO), System Rescue CD, SuperGrub disk, Rescatux, Grub-customizer (not live CD), etc...
And of course, as it's a double boot, you can use the Windows method (I consider the Linux one as safer through).
It's not confusing, there are several methods to do that. You can use the Windows MBR restauration at the condition your Linux disk is unplugged, and then, you will have a fully functional Windows MBR. In this case, it won't be a dual boot, but you will tell that you want to boot from the disk or from the removable media, alternatively.
More info: https://help.ubuntu.com/community/Grub2/Installing#via_the_LiveCD_terminal
Next time, to avoid this kind of problem, follow the recommendations:
nstalling Ubuntu to a Specific Partition ("Something Else"):
*When using the "Something Else" option, you will be offered to choose the "Device for bootloader installation". Please select: * either the disk (eg /dev/sdX, not /dev/sdXY) on which the BIOS is setup to boot (recommended for normal use) * OR the partition (eg /dev/sdXY, not /dev/sdX) on which Ubuntu (/boot, else /) will be installed (only if you want to chainload it from another bootloader; if any doubt, do NOT choose this)*
Never choose any other partition! (this may break the boot of your other systems, see Bug #1049549).
On a system with multiple drives and OS's, the user can preserve the original bootloader by installing GRUB 2 on another drive. To accomplish this:
specify the disk (eg /dev/sdX, not /dev/sdaXY) not currently used to boot the system for the bootloader location.
After the installation is complete, change the boot order (via BIOS setup) so that the disk to which the GRUB information was written is the one booted first.
If the user wishes to restore booting with the original bootloader, change the boot order back to the original drive.
GRUB 2 normally writes its bootloader information to an area just beyond the Master Boot Record and before the first partition. Some software on non-Linux operating systems also used this embedded area and broke the system by overwriting the GRUB 2 information on dual-boot systems. GRUB 2 now can recognize this potential problem and avoid it.
The bootloader information does not have to be installed to the embedded area of the MBR. It may also bypass the MBR entirely and be installed to a specific partition. In doing this, the location of the GRUB 2 files are specified by using blocklists. This option is not available via an Ubuntu GUI installation but can be made via the terminal after installation. Even then this method is not as reliable as writing to the MBR and is not recommended by the GRUB developers.
Fixing with the Windows method:
https://www.pagestart.com/repairwin7dualboot02.html
With a Windows CD/USB: Choose “Install Now”, and then "Repair your computer'
System recovery options >> Command prompt >> Diskpart
Tuto here
bootrec.exe /fixmbr
bootrec.exe /fixboot
bootrec.exe /RebuildBcd
