Here's a scenario: the installer prompts the user if this shall be a system-wide installation for all users, or a local installation for one user. System-wide installations will be the default, and support all the Windows standards and recommendations. A "local" installation will be just like the current default behavior, with the data files in the same directory as the executable.
Not sure i agree with your logic there, the correct installer options in such programs are more along the lines of 'for this user only', 'for all users'. Where 'for this user only' uses the users application data folder, and 'for all users' uses the 'all users' application data folder.
I think mirc should have a little more flexibility than that however, the options should include...
- install and configure to use the users application data folder (default)
- install and configure to use the all users application data folder
- install and configure to use a self contained folder (all files in the mirc executable/installation folder
All corresponding shortcuts (if any) that are made should reflect this with use of the -r flag when neccersary.
When upgrading, mirc should not move your application data anywhere unless you specifically tell it to, have it selected by default if you want, but makes sure you are able to turn it off so that an upgrade leaves the files alone (apart from baking up to /backup/ if required of corse)
I personally prefer such programs as mirc to be self contained, it is often neccersary to larger programs for shared files and application data to be seperate from the binaries, but this is not the case with small programs, therefor it should not be forced during the installation. (i often backup mirc and other smaller utilities that are used on a daily basis, which as you can guess is partially why i prefer to use the self contained method)