C# scheduled jobs

For a C# 2010 windows service I need to check to see if files exist in a speciifed directory location at specified time intervals. If file(s) exist in the specified location, I need to accomplish the following steps:
1. I need to call some specified code for updating the database,
2. I need to  find a way to indicate the files where already accessed without moving the files from their original location.   
3. I need to know how to setup the windows  service.                                                                                          

Thus I am wondering if you can tell me and/or point me to a reference that will tell me how to accomplish my goal using a windows service? I could use a different utility if you think it is better than use a windows service.