Thank you... I am checking it now.
Whilst it is true i have not checked out these forums I have looked at a couple of tutorials and the y seem to make no mention of how to actually open them.
The catch is, you don't open the actual bitmaps in the texture folders because they are (usually, as in the default aircraft) in a non-standard bitmap format.
That's why you'll use a program like DXTBMP to convert the bitmap to a "regular" bitmap you can open in Photoshop, Paint Shop Pro, etc.
Abacus' FS Repaint is the only paint program I know of that can open the bitmaps directly and allow you to repaint them.