CommonApplicationData folder access is denied in Vista to a Service

I have written a windows service that stores configuration settings in an XML file.  I use to store the settings xml file in the program's folder however Vista's new security model does not allow this.  The service runs for all users and should behave the same way for all users since it runs unattended (without a user logging on).  After researching the folder to store shared user data in I found that I should be saving data here:
Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData)

When my service runs howerver I get the exception:
Service cannot be started. System.UnauthorizedAccessException: Access to the path 'I:\ProgramData\settings.xml' is denied.

My questions is - is this the correct directoy to store application specific data in and if so how do I use the Setup Project to give proper permission durring setup to this folder.  If not, where should I write the settings for the service.  Keep in mind that the service writes default settings if they do not exist and normally reads the setings on start.  A seperate exe must write changes to the settings.