Bart De Smet's on-line blog (0x2B | ~0x2B, that's the question)
Just to illustrate how popular the question is actually. The next question I was answering was basically the same (but now for PDF file protection) :-): http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=692594#692617
good thinking :-)
Do you have more detailed code of rendering the file as Binary? We're having to use this protection scheme for files now, but I haven't had much experieince with ouputting to the binary stream in ASP.NET, and I've having a bear of a time getting this to wrok.