The autoplay on my computer always run Windows Movie Maker when I plugin the firewire of my Sony DV. I had no choice of turning it off or change it to another program. Here is a way how I finally changed it.
use regedit, goto HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers\EventHandlers,
you will see an entry: VideoCameraArrival, with a key "MSVideoCameraArrival" with no value. This handler is defined in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers\Handlers.
So all I needed to do is to add a key "MyVideoHandler" to the key VideoCameraArrival, next to MSVideoCameraArrival, then define MyVideoHandler in 'Handlers', with the contents of:
Action: "YOUR PROGRAM PATH"
initCmdLine: "YOUR PROGRAM PATH"
That did the trick. Now when I plug in my DV, windows asks me which handler to use. I can pick either.