how can i transfer the movie to my computer?

the usb was already connected but.. there's a message "please insert ac adaptor" i don't understand... the model is PANASONIC VDR-D200GT.. please help me

You need to connect the AC adapter to the camera, I suspect. If you want to shoot video and then edit it to take out wasted scenes, add titles and music, etc., you're taking a hit in video quality by shooting native with a DVD camera. This is because the video on DVDs is encoded to MPEG2, a compressed format. It's great as an end of the line format, but not for shooting source footage. Likewise, hard drive based camcorders, while convenient, tend to record in MPEG2 (only JVC gives you an option to record in AVI). This gives you the same problem. Additionally, if your editor doesn't import MPEG2 footage, you will have to "re-encode" (also called demuxing) the footage into an editable format. It's a hassle for those of us who wish to edit our videos as a hobby.

However, for DVDs, you'll need to take that DVD and "rip" it to your PC and then encode it into a more editible format. I recommend DVD Decrypter or DVD Shrink. They will get your footage off the dvd and onto your PC. You can then use something like Videoera (PC) or Handbrake (Mac) to encode it to a more editable format. Depending on what editing software you use, you may be able to import mpeg2 and even VOB files directly. But understand that you're already starting with compressed footage, so the resolution quality will not be as good as if you had shot native with MiniDV tape and captured to your PC.

Good luck.