> again I think this is rather cumbersome unless it is one monster exe. I would test to see how long it takes to download on average, and give a window saying "Please wait 20 seconds while a new copy of your application is downloaded" or something, with an hourglass so they know something is going on...

Well, LLFF approach with copying a large file in 32K chunks would give enough speed and time to update the progressbar, without much of a delay. Anyway, having such a copy operation running in a separate thread would be prone to errors, because the launcher would receive "finished" message before the copying is actually accomplished (and seems to be that "Copy file" command is doing so).