Well the way I have done it is to create a webservice which your application calls, sending it information about itself, then the webservice would detect on the server if there is a newer version and if so, it will take the bytes[] of the new version and send it across to the client (your "old" application)

I dont think there is a way of doing it "over the net" like Windows Update for example.

in order to create a webservice, I am unsure if the WebDeveloper Express edition of VS2005 has this option, but it is available in the full version of VS2005 (or VS2003)