You are correct the backup is specific to the computer that made it. This was true in the past and I have not heard of it changing.
However, I think you still can download a copy of windows that you make a cd of and install windows on any computer. I do not have a link but google should help you find it. (At least this is what I've read.) You might snoop around the following site, it is loaded with 10 info.
https://www.tenforums.com/