allowDomain doesn't give you access to other domains, it allows other domains to access you. You can only open the door to your own house, not somebody elses.
A SWF served over HTTP cannot access the local file system so trying to get the image from the D: is not possible, plus it refers to the user's D: drive, not yours. If the image is small, embed it and pass in the class name.
Flex SDK Developer
Adobe Systems Inc.