Hello,

       Yersterday I bought the PMDG 777.Keeping internet connected,when I installed the PMDG 777,started FSX and loaded the PMDG777 plane, no activation window appeared. How can I active the PMDG 777,thanks very much.

http://support.precisionmanuals.com/Main/Default.aspx

Register there and create a support ticket. PMDG will verify your details and once they've confirmed you have purchased the aircraft, they will sort you out.