Writing to a 4.5GB DVD is pretty slow, and you will probably have to [i]span[/i] your backup over more than one DVD. Restoration from such a configuration is a nail-biter.
I have used Norton Ghost:
http://www.symantec.com/norton/products/overview.jsp?pcid=br&pvid=ghost14
and it has performed seamlessly for me on multiple occasions where I was desperate to retrieve an imaged backup.
Ghost will directly write an [i]image[/i] of your drive to the external hard drive. Should you ever need to restore the computer from the image file, Ghost will overwrite the native HD at 1-2GB/min, and you'll be totally recovered in <20 minutes.
I have no personal experience with [i]Acronis[/i], but if Peconet Tietokoneet endorses it, you can trust his authority.
Rick/Portland, OR