The applications ARCHOS Music and ARCHOS Video automatically detect your files once they are transfered to your device. To do so, you need to launch the application to scan your device. You will see your files displayed in the carousel and can choose to display only those files that have been recently added.
The application Gallery works the same way, it automatically scans all your pictures on your device everytime you launch the application. Every type of files is scanned: photos taken with your device's camera, screenshots, images you automatically transfered or received via email and then saved.
All these files can be manually saved by connecting your device to your computer via USB. These files are stored by default on the folders:
Videos : Movies
Musics : Music
Photos : Pictures
Photos/Videos taken by your device : DCIM/Camera
Files received via Bluetooth : Bluetooth
Files saved (e-mail, browser ect...) : Download
All your files can be synchronized with Windows® Media Player (version 11 or later) or iTunes®. the synchronisation only works if your device is connected as a multimedia device.