Bon, j'ai trouvé une réponse en version longue, mais en anglais 
Video palyback will work either way, but with a few limitations. If you simply want to clone your disply on the TV, uncheck the "extend my windows desktop" box on the first page of the display properties>settings page. Then go to Advanced>Displays and enable the TV display by clicking on the button. Make your TV the primary display and your Monitor the secondary display. This will maintain your monitors refresh rate and size while outputting to the TV as well. The TV has to be primary in order to see the hardware overlay video on it. If you want to view the Video on your monitor, simply reverse these settings. I saved these settings to a scheme so I can quickly flip between them from the desktop tray icon.
If you want the secondary display to be independent, go to the first screen of the Display properties>settings and click on monitor 2 at the top of the screen. Make sure that the "extend... " checkbox is clicked. The reason you can't drag the ATI file player is that as long as the Monitor 2 (in this case the TV) is a secondary display, you will be playing back through software, not through an overlay. The file player requires the overlay for playback, hence no dragging or display on the secondary display. Despite this, you CAN play video on the extended secondary display using a player such as Zoom Player or Sasami2k. It depends on the type of media you are playing back. I have found that on my 1.4 Athlon, Divx and other MPEG4 movies look SO MUCH BETTER playing through software than with the overlay. Much less macroblocking and a generally better image quality. So these settings are perfect for my playback needs. Go figure.
If you are trying to play back DVD, it is a little trickier. Obviously, you would rather use the overlay to be able to access all of the hardware decoding features of the card. This is where Hydravision is supposed to enter the picture and allow dynamic switching of the primary/secondary monitor. Unfortunately, this is still crippled in WinXP. So instead, you need to uncheck the extend box for the secondary display, reverse the primary / secondary buttons either form a pre-saved scheme or from the ATI displays tab, then reenable extending the desktop. Now, however, there is another problem b/c the TV is considered the primary so all of your icons and the taskbar are on the TV while the monitor is blank. This can sort of be fixed by saving a desktop under the multidesk tray icon, but it is overall a PIA at best. If you didn,t mind complete software DVD playback, ignore this and simply leave it set up as described for Divx playback in the previous paragraph, but depending on the player YMMV.
If anyone knows of a better way of doing this, I would love to hear it. I have fiddled with these settings for quite some time know, and this is the best I can come up with. Basically, I am waiting for ATI to get their heads out of thier collective asses and GIVE ME HYDRAVISION FOR XP!!!!!!!!!!!!!!!!!!
En résumé l'overlay n'est disponible que sur la sortie principale, mais on peux lire les divx sans l'overlay avec Zoom Player ou Sasami2k. Sinon il faut basculer la TV en sortie principale, le moniteur conserve heureusement sa résolution et fréquence originales sur la seconde sortie, mais la barre des taches se retrouve sur la TV. C'est d'ailleurs le seul moyen pour visionner les DVDs, sous XP au moins. Ca marche donc à peu prés, mais l'Hydravision devrait être améliorée dans les prochains drivers...
Voilà, pour ceux que ça interesse...
moi aussi cela m'interresse
sur ton moniteur en sortie secondaire, mais pas de jeux 3D, et faut rajouter une deuxième barre de tache sur le moniteur.
