Why does Windows move its bootloader to another drive during installation?

Question

Windows

I decided to update the faithful Samsung 300v5a-s08 laptop: 8 GB of RAM, 250 SSD and a terabyte HDD. The SSD was stuck in place of the old screw, and the terabyte drive was installed through an adapter instead of a drive.
I wanted to install systems from scratch, of course, on an SSD, of course, via a USB flash drive. Ubuntu got up easily, but Windows stubbornly refuses (you need a dual block).
I put both seven and eight - no way. Files are copied, installation, the first reboot - and a black screen, only the backlight turns on and off periodically.
Then I discovered an interesting feature - it turns out that Windows reserves the system partition on a terabyte (350 Mb) and puts its bootloader there (~25Mb in size).
Further, if you boot Ubuntu from a LiveCD, set the boot flag to the Linux partition, then grub appears with a choice: Ubuntu or Windows from a terabyte. That is, contrary to common practice, grub is not overwritten.
It is even more interesting that the figure eight stood up normally in this way. But the seven, which I need to install, since I have a license for it, writes that installation on such a computer configuration cannot be continued.
My BIOS is very short. Of all the settings: UEFI Boot Support - cut down, and AHCI mode - manual and auto.
The questions are:
Why is this happening? And
how can this problem be solved? And I would like to solve it without pulling out the HDD.
UPD. Pulled out the HDD, everything fell as it should. Thanks for answers. In case of rearrangement, will cloning save you from a screwdriver?
Faced another problem - the sticker was worn out. Went to google...

Answer 1

Perhaps due to the fact that the HDD sits in front of the SSD on the bus. Popping out the HDD seems to be the easiest solution, but you can still try to overwrite the bootloader on the SSD after installing Windows. And it is better to install Windows first, and then ubuntu.