Originally Posted by skai
roebeet, I don't know if this is the same thing as sleep mode, but I use it all the time on my D3. If you press the (power) hold button twice within 2 secs, the device locks and the screen goes off. The good thing about this is that any music you have playing will still work, and the next, previous, and pause buttons still work. Once you pause a song in this mode you will need to turn the device back on first before being able to use the hard buttons again.
skai, you're right. From page 8 of the Cowon D3 user manual:
"3. Sleep Mode: Within 2 seconds of entering into hold status, pressing the Power / Hold button again changes the device to lock screen status. With this status, waiting for a couple of seconds or pressing the Power / Hold button once again turns the device into sleep mode"
A deep sleep mode would be great for overnight if you're not near a charger, but I've kept mine in sleep mode overnight and woke up with plenty of battery for the day.