Hey
VERY common problem in repainting. I had it too. The FS9 bmps are in a different format from regular bmps. Meaning you have to download DXTbmp from simV to open the files.

Once you'v done that then you just open the file in DXTbmp then convert it to 24bit bitmap. Then you MUST remember to save it as either a 32bit bitmap or extended in DXTbmp before you open the aircraft or the textures wont work.

If you look through the topics in this froum you'll find a link to DXTmp

hope that helps
forfun