You have two choices (at least I can suggest two):
1) Add custom action to your installation package that will change file permissions to allow everyone (or some specific users) to access your file
Take a look at FileInfo.GetAccessControl and FileSecurity.AddAccessRule classes/methods
2) to always ask for administrator rights you just have to update app.manifest file with appropriate tags, see
http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/da5a8665-70da-43b0-b67d-5cfc9ff0c972[
^] for more details