I have a(n) HDD External Western Digital Hard Drive, can I plug it to my 360 Elite, and copy files? Easy 10PTS?

I have an old 20 GB Hard Drive, but now I have a 120 GB with this new Elite, I do not want to buy a transfer cable, or memory card. Can I plug my HDD External Hard drive to the sys. then Copy it on there. And then plug the other hard drive, and Paste it on there????