Installing Caelinux, right, but I still made a mess

CaeLinux is based on Ubuntu. I`ll use it for learning and 3-print ideas. I managed to install the program, but I erased my Windows 7 hard drive by accident, like this. I installed from a USB-stick to a USB hard drive. I thought, by doing this I could erase that old hard drive at the same time. I guess this was wrong. It seems as the computers hard drive was erased as well. Maybe not irreversible, but it probably became that after my intuitive fixing. I tried to use a stored copy with rescue, but my laptop did not recognize it. Then I went for reinstalling the original system, but I still can`t get it back to where it was. Anyway, this is a Windows problem. For this case the problem is that my Ubuntu USB hard drive don`t work alone. It was obviously dependent on some files or pointers on the computers hard drive that I wiped for reinstalling.

I guess it is a basic solution to this.
I need something to direct the computers attention to the Ubuntu hard drive as such. I suppose my machines supports the possibility to choose from different systems, but how to do this manually? -without reinstalling. The CaeLinux drive was just fine, and I guess every thing, except the direction to it, is put on this. My first thought was to put the new Ubuntu system onto another old computer, after the installation, but I`ll get the same problem there.
(I find my reactions quite reasonable. If I install a operative system to a hard drive, it would be reasonable to think that it could work for it selves, and that only this hard drive get wiped. If not, I could have been told so by the instructions.)

I hope someone can lead me to a easy fix.

For someone trying to save the world, read this first:)
https://www.arkitekt.se/wp-content/uploads/2016/06/64.-Sustainable-culture-is-more-on-tager-.pdf