EmelFM2 file manager will rename the files however you want (don't recall if it handles .xxx files, but it does let you rename extensions)
The Maemo5 version is still in the Extras-devel repository so it is not quite ready, but once it makes it into "extras" I would recommend installing it.
The tracker method pointed to by codeMonkey appears to be the cleanest solution to hiding media files that you don't want indexed.
Seems the way to go... if it works, which I haven't tried.
EDIT:
Try to play with this section... looks promising:
Look how they include $HOME/MyDocs/.sounds/ but exclude $HOME/MyDocs/.sounds/Ringtones/
You could do the same, have $HOME/MyDocs/.videos/ in the "watch"-list (where it is now), create a new folder "private" in there and then include $HOME/MyDocs/.videos/private to the NoWatchDirectory= line.
I have also mentioned this for the image/gallery viewer. It finds all images on the phone. I'd installed some WRT (web runtime toolkit) HTML samples with images and it cluttered up my imageviewer. I have allready suggested this in 'update fixes', to be able to have a set folder for these kind of apps, like images or video, for display in their viewers/managers.
I got my n900 on friday and one of the first apps i installed was Truecrypt. i have a 3.5gig encrypted container on my sd card that i use to store my 'delicates'
this is much better than just hiding as it totally encrypts them so if you lose your phone the data is still safe.
best of all its crossplatform. I can plugin my phone and mount the container in windows or linux and transfer directly to the encrypted container.
There's a very simple solution that doesn't require modifying any files and allows you to view the files through the normal File Manager application.
(1) Put your files in a folder named Private.
(2) Done.
The default Tracker configuration exempts directories named Private from indexing, so they don't show up in Tracker-using software (media player, photos, etc).
