Electronic Software Delivery (ESD) using .Net

[Mike]

I need to add secure ESD to our store -- basically restrict the download of
certain files to only customers that have purchased. Seems like a common
store component yet I can't seem to find any articles, examples, or
discussions to give my development cycle a kick start. If anyone has any
pointers to such resources I'd greatly appreciate a url or two.

I have a number of ideas but would like to hear/read of anyone else's trials
and tribulations before starting from scratch.

Thanks,
Mike