email notification with due date

I am tired browsing and searching internet regarding on how to email notification by due date. I almost tried to understand the tutorials for two weeks but still, there is no process. I need to send an email to the user to comply with his requirements after 1week. I am developing a website (visual c# settings) using visual studio 2008. I don't know how to call windows service using my website. I do the basic email notification but with due date, I really having a hard time. I am a newbie to windows service so I hope u understand. I hope anyone who could provide me with the codes regarding this. Thank you,
...