To open the textures: DXTBmp
Unfortunately DXTBmp only opens the file so you can't edit with it you have to use another editing program to do that. By defult it is MS Paint but you can set it to any program you like. I use Paint.NET for the editing. When you first open a .dds in DXTBmp you have to flip it before you send it to your editing program. A tip that I learnt from Patchz was to open it in DXTBmp then send it to the editor & save as a different file otherwise it gets pixelated.