How do you edit a little bit of texture in fs2002 in paint without the whole texture disappearing?

There's some add-on planes for fs2002 that I have that just won't let me edit the textures. The littlest dot that I make, and the whole texture disappears in the game. I was able to edit a texture on my spitfire on my old computer by I can't on this one. Is there a way that I can do it, or trick the game into taking the texture or something?How do you edit a little bit of texture in fs2002 in paint without the whole texture disappearing?
it depends on ur computer