If you have an unmountable/unrepairable HFS external drive, you can try using Mediafour's MacDrive running on Windows to access the data. This is my story...
My external FireWire HFS drive stopped mounting on OS X after my kid unplugged it while writing was in progress. I tried various products to restore it, including Disk Utility, DiskWarrior, DataRescue, and SystemWorks. All in vain -- even in the most advanced mode of DataRescue.
I gave up and was ready to repartition/reformat the disk for use with a Windows XP notebook, so I connected the drive to the notebook. To my surprise, MacDrive woke up and mounted the drive. MacDrive complained that the last time the drive was used it was not closed properly. Ultimately though , I was able to copy all contents I needed before reformatting the drive.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060127200824889