DXTBMP replacement

Hello there. I'm a long time user of the app DXTBMP http://www.mwgfx.co.uk/programs/dxtbmp.htm which I use to view aircraft textures in FS9/FSX/P3D. I have tried to open them with GIMP, Irfanview but neither can display the texture properly. (Irfanview can open the file, but its all distorted and not readable)

I think they are Extended BMP textures DDS/DXT with Alpha channel, whatever that means

Does any forum member know of a program like DXTBMP that will run on Portable Apps and open these texture files as if they were a normal image?

Many thanks,

Chris Morgan