Ok i reloaded it, its the same as your version i saved as DDS my computer cannot tell what the file is, i looked at the other folders they dont appear to have DDS
Bob. Unless this is an FSX default aircraft it's quite likely the textures are not in DDS format. My advice with repaints is to save edited textures in their original format. The format will be displayed on the blue bar (above the menu bar) when you first open an unedited texture in DXTBmp. The example below is a 16 bit Extended Bitmap in DXT3 format.

You can always change this later if there is a problem.