isn't one of the command line functions of cscript and vbscript to reassociate the extensions back to default. If so, changing the defaults may not 'stick' to a well designed script virus... dunno, haven't tried it.
What we do (and I suppose most networks SHOULD do) is to block exe, bat, cmd, and some others from going through the mail server. Of course, that doesn't stop someone from going to hotmail, or sneakernetting exe's, or hyperlinks to those types.
I suppose that a simple thing you could do replace wscript and cscript with notepad during\upon receipt of notification of the latest and greatest script virus... until your AV definitions are updated, then replace the copies with the originals (assuming you use wscript functions regularly)
Nothing is going to be as foolproof as a well maintained AV software... (and basic filtering on the mail server)
like one of my instructors said... "How important is your data?"
