Load up a suitable walk as normal ignoring how the arms look. Just get the legs working the way you want. Now open up the animation window and delete all the key frames for the arms and hands. Next go to frame one and pose the arms. You'll now find that the arms will stay put but the legs will still walk. If I'm lucky I'll be able to attack the file to this post. Right click on the link and save. Then in Windows Explorer remove the TXT extension.