We've written an application that works fairly well in XP, but is having serious migration issues to Vista and Windows 7, probably due to where user data is being written.
The use case is this: Individual users need to log in to the machine and use it to acquire data. Supervisor users need to be able to look over the shoulder of individual users and verify that they're performing their jobs properly. These supervisors also need to check system logs to make sure that the system is performing properly.
The way that we accomplished these tasks in XP was to write to a folder on the C:\ drive directly. Maybe that's bad practice, maybe it isn't, but basically all users of the system needed to be able to access this data as shared data. In some installations of the program, the IT situation was just not secure at all, and there was a single user for the computer, and then each individual logged in to our program separately. In other installations of the program, the IT staff is competent and has different logins for different users, but each user can still access C: and each user can still check other users as necessary.
In Vista/Windows 7, that all changes. If the IT staff locks everything down to individual users, these users still need to share this common data, and writing application-specific configuration parameters and user lists to the directory of the application is just not allowed. If the system is in a location with a domain, then the user does not have local admin rights, and even installation could be a problem.
Is the solution to this to have the installer make a directory that every user can write to, and then put all user-specific data in that directory? If so, is it possible to have an installer behave that way (even if it has to be given admin rights)? Or is there a way to make Vista/7 behave in the more liberal XP fashion?
The most definitive resource is the "Data and Settings Management in the Application Specification for each windows version in MSDN. Read this to see the rationale behind the various special folders that exist on Windows, and how to choose which one to write data to.
Next, your application would need to use the SHGetSpecialFolderLocation API to retrieve the paths to the special location.
The folder that most likley serves your needs - being written to by one user, read by administrators, would be CSIDL_APPDATA - which, on Windows 6.X, corresponds to C:\ProgramData\
By default the rights on folders created in this location are full control for administrators and owners (i.e. the user that created it) and read only access to members of the Users group.
A completely seperate excercise is writing the code necessary to modify Access Control Lists (ACLs) on Directories. One that will be necessary if the defaults rights on your chosen location arn't sufficient for your purposes.