Another new thing in DirectX 10 is that the format of the file-header changed from using Four-Character-Codes (FourCC) to something Microsoft calls DXGI header which has extended information on the pixel format of the file. This is what trips up 3DSMax and Photoshop (and Gimp). (..)
If you just want to view those textures I recommend PicoPixel which can view any .dds subformat there currently is.
If you want to edit the textures you can use Microsoft's texconvcommand-line tool to convert them from .dds back to another format like .png. Just keep in mind that .dds compression is lossy, so round-trip conversions (dds → png → dds) loose some image quality even if you don't edit the .png. Keep the .png (or whatever) if you plan to make further changes in the future and only convert to .dds as a final step to get the textures into the game.
I've opened some files in Visual Studio which also worked fine, but that would of course be overkill just to view/edit a few textures.