If you decide to use this solution and use a UNC path, I beleive it would basically be specifying the UNC path in a URI, e.g.

file:///servername-here/sharename-here
[download]

keep in mind that UNC paths only work in IE, at least so far as I've tested. I have a site that I've had to do that, and found that it doesn't work in Firefox on Windows or Mac. I haven't tried other browsers, but I suppose you may be able to use Opera, but it may have to be IE compatibility mode.

Also, you may have to use javascript to launch show.exe from the UNC path (this is assuming, again, that you want it on the client side).