I plug NWA3000 into the computer to change music,

Try resetting the device it?s usually a small pinhole on the back or side of the device try holding that in for about 10 seconds or Try reflashing the firmware for your device you can find the latest firmware and flashing utilities from the manufacturer?s website. Make sure that you back your music up first because when you do this you are setting it back to factory settings. then us: If you have a large playlist to transfer, you may prefer to do it from your media player, such as Windows Media Player. Once your MP3 player is connected to the computer, open Windows Media Player. Click on the "Sync Music" tab. Drag songs that you want from your Windows Media Library over to the "Sync Music" column to create a playlist. Click the "Begin Sync" tab at the bottom once you have all of the songs on your playlist. This action will sync all of the songs to your MP3 player with one click. Disconnect your device once songs have been transferred by clicking on the "Safely Remove Hardware" icon in the bottom-right side of the desktop tray.