If you just plug your Motorola Droid into your Windows computer it will not see the DROID. This is how to transfer files back and forth from our DROID.
1. Connect you DROID by USB cable to your computer.
2. You must mount the DROID.
To mount the USB drive in Windows, pull down the notification menu (drag your finger down across the top on the screen), choose “USB Storage”, and then choose “Mount”. This allows you to place the SD card in your phone as a drive in your computer. This will makie it easy to transfer files from your PC to your Motorola Droid and vice versa.
3. Just drag your files back and forth just like you normally would with a windows device.
4. To keep thing organized just add new folders to your SD card. Folders named Music, Videos will make it easy for you to find them and your DROID will auto recognize your music and video file when you turn on your phone.