(See also MovieOS)
(This is mostly based on what I learned from discussions in Slashdot...)
The Hollywoodware in these days are usually created using programs like Macromedia's Director. In computer program design world the programs shown in movies might be called "computerized paper prototypes".
The reason behind this is that while you could in theory use real applications and teach the actors to use the programs, they would not work too reliably.
For instance, imagine using a web browser when cameras are rolling.
Actor: (types in the URL and hits Enter)... (waits some moments) (somewhat out-of-character:) "The damn site is slow again..."
Director: "Okay... CUT! Everybody, let's try again. What is it, Take 32?..."
...just what happens with my 'net connections every day, all the way from 28.8k modem to DSL... Realism, yes, but the movies potray the perfect world where everything works just fine. =)
No, what the art creators want is apps that work just fine and the actors only need to press buttons (or whatever) to get to the next part of the "multimedia show".
Now, when computers don't work they tend to get stressing (as everyone has probably proven - hugely non-working programs tick me off, no matter what OS I'm using); this sort of faking makes shooting the film much more pleasant for everybody.
Now, what the directors and producers usually want is "something that looks cool". If there's a real application or widget that looks surprisingly cool, they'll use those usually as they are. If it doesn't, they will want something fake that looks cool. (Example: IIRC, the producers of The Saint really wanted to show Nokia 9000 Communicator because they saw it and thought that was a really futuristic and cool-looking widget (which it was, at the time - and of course, perharps Nokia's "cooperation" helped to come to that conclusion too)... the application shown in it was faked, though, because the apps that come with it are sort of boring again.)