Get linux, then all you need is chmod.
create a directory called "portable" in the top ...
Once you had those two directories, portable and the original one,
I found a simple solution: It seems that the ability to modify is linked to the directory the files are in.So if I copy them to another directory, I can modify and copy back.
No "portable" is actually a magic directory name.
I suspect it is an incredibly small percentage of privately owned PCs and laptops that are used by more than one person and where those people need to be protected from each other.