wattbatt

I just let it save with the first it came up with which was BC1 (Linear, DXT1) I cannot get to use that texdiag thing. It's a command line operation right? I downloaded it ran the exe then typed texdiag into command line but it says command not recognized

I have a .dds image, I just want to move it on the canvas (it's at the bottom and i want to move it somewhere else) It's kind of a faint white aura, a bit transparent. I select it and use the move selected pixels tool. But after doing my thing and saving, it goes bad. Do I have to change something in how the file is saved? Images: before and after saving