image.dd file of a corrupted EXternal HD , looking to mount/recover ?

I have a 500gb external hard drive that failed to be recognized and the files are corrupted . I have created a raw image of the entire drive and saved it as a image.dd file onto an different external hard drive. I know that the raw image is just a mirror of the original corrupted drive. But now what is the next best step to recovery a much data as I can ? Any concrete steps would be greatly appreciated

Right now I have a laptop that runs on vista and a PC that is Windows 7. I can use either one to attempt a recovery. Thanks

 

I did these steps, created an image.dd file and attempted to use osfmount . I was sure to "uncheck" the read-only box . But when I clicked on the mounted drive it said G:\ is not accessible The file or directory is corrupted and unreadable. Please help