I don't think that can be achieved in the way you would like to have it.
As you probably noticed yourself, it's easy to install the application in such a way that it is accessible from all Windows user accounts. But the logon information is bound to each specific account. This makes it possible for multiple users to each have their own Spotifiy, for example.
So, if you wish to share your Spotify account (which I doubt is covered by the Spotify license), you have to provide your logon data to the other user.
Of course, you could just be with the other user when he is logged on and then enter the password yourself, thus not revealing it. User B would now be given full access to your Spotify account, including the possibility to change the password. And like I said, you could run into license issues and risk blocking your account.
Just use Spotify the way the company intended: Create a separate login for each user, then share your music with them from within Spotify. Unless User B wants to listen to lots of ads, this won't come for free, but you might be eligible for a Spotify Family Plan.
I don't know Picasa well enough but I'm pretty sure it's similar.
Windows includes a Public folder, located at C:\Users, which is accessible to all users. If you save files in this folder, it can be shared among all the users. If you want to create and save files so that you can share them with the other users, you should save them in the Public folder. – Phoebeli – 2016-01-09T15:10:37.220
its not so much about sharing files. – Olav – 2016-01-09T18:39:18.533
What I want is the same experience as if B used Spotify as me. – Olav – 2016-01-09T18:48:31.300
2This is handled by installing applications as an Administrator. In most cases an application provides an option to only install it for the current user or for all users. The
install for all users
option requires Administrator privileges. – Ramhound – 2016-01-10T09:42:27.200