I had an old 80GB USB external drive. I attached it and Windows would not open the drive, saying it had to be formatted. I opened Disk Management and it said the disk was RAW. I scanned the drive with Testdisk and a Partition Manager with no results. In fact Testdisk said the file system was damaged. For some reason the partition manager showed it as formatted NTFS with some data and I was a little concerned on what was on the drive.
I figured what do I have to lose so I booted my old computer with Ubuntu, attached the USB drive and low and behold it mounted the drive without a hiccup. I browsed the drive and only recycle bin/system restore data was on the disk so I launched Gparted, deleted the partition table and reformatted the drive.
Moral of the story? If your disk shows RAW and Windows fails to open it give linux a try.