just a thought...

how about eliminating filename and extensions altogether instead? replace them with meta tags and replace shell with one that support querying on metadata. build explorer on top of that shell.

with that in place we can then look for a document by having a query like:
> 'list (all) with tags (and/or attributes) 'presentation slideshow on company sales presented two days ago'
-- 2 items found
> select first

and boom i got the presentation opened with the appropriate app.

i was kinda hoping that WinFS will enable this kind of scenarios. but then again,... its been ages since we heard anything.

Edit: bad grammar deshita