If you are going to give that dpmagic a go make sure you go for the 'minilab' version as that shows its compatable with the later Canon RAW files (although not listing the 40D).
Its probably your best chance
Your only other (slim) chance is doing a registry hack. Going back a while before MS released their thumbnailer application there was a registry hack that associated a .dll file for the Canon raw format with windows explorer. If you can find that, and the relevant .dll (its already likely to be installed if you can view thumbnails in other apps) for the latest RAW files it may be possible to work something out. Obviously if you try this, back up your registry first in case you have issues.
