| Store non-essential user data in the local Application Data folder |
Sometimes the data you have just won’t fit easily into any category, or more likely fits into several. Consider settings that are specific to both a User and a Machine. Where do they belong?
Well, settings that are specific to both machine and user should be placed in CSIDL_LOCAL_APPDATA, which is non-roaming (When writing to CSIDL_LOCAL_APPDATA, you should always append \Software\CompanyName\Application\Version to the path).
It’s important that you don’t confuse this with settings that are specific to a machine but common to all users. These types of settings belong elsewhere (the guidelines for these types are discussed in other sections).
A good example of a setting that is user and machine specific is a game that allows each player to select the default-input device for the user. The options on one machine might include a force-feedback joystick, keyboard, and mouse, while another machine might have a normal joystick, keyboard and mouse. This kind of scenario is rare but important.
CSIDL_LOCAL_APPDATA is also a great place to store non-essential user data. Typically these are things that you’d like to have roamed, but just didn’t have the space for in your roaming profile. Stuff like Window sizes and positions; things that’d be cool to have but that would just add too much of a penalty to your roaming performance.
Appending Version number to the CSIDL_LOCAL_APPDATA path is optional, but is always a good idea to help better handle upgrades.
CSIDLs, Registry Overview, SHGetFolderPath, Store application specific data to HKEY_LOCAL_MACHINE, Store user settings in the user's profile