As I have debugged problems in com, side by side, dealt with dll hell, all while hating the windows registry with passion, I was wondering why is it needed.

I never felt compelled to read an entire book on registry best practices, and then just "get it".

I have, however, used Linux and Mac OS, and look at the ways one can install multiple versions of Python and its libraries on the same *nix computer.

Because registry has somewhat of a free (albeit ugly) format, and is used for all sorts of purposes, I have never understood what essential problem it is trying to solve.

For instance, Microsoft does not want you to have two different versions of MS Office installed side by side. They use registry to enforce this during installation. This limitation is artificial, in my opinion. If they really cared to allow a different behavior, they could have adjusted their architecture accordingly.

In Mac OS you can install and remove apps by just dropping them into a particular folder.

So,

A) What essential problem it is trying to solve? B) How do other operating systems solve it?