Opening html file in windows form

Hello, I'm wanting to add a help file to my app that I'm writing using Visual C# Express. My idea was to open a web browser on a form and displaying the help file in the browser. I've put the help file in the same directory as the rest of my forms, and set the URL property to http://filename. However, my app can't find the file. Am I setting path wrong? How do I correct that?