Generating RDP files on web server fails on save

When trying to generate rdp files on a web server with C#, when I try to save the rdp file it always fails with access denied.  ASPNET and Network Services has full access, and even added EVERYONE as full permissions and it still won't save any ideas?
 
StringBuilder newFile = new StringBuilder();
            string temp = "";
            string[] fileToUpdate = File.ReadAllLines(filePath);
            foreach (string line in fileToUpdate)
            {
                if (line.Contains("full address:s:"))
                ...