1) Open the .mdl in med.--> go to skin manager --> go to skin settings --> go to texture file --> Make sure "extern" is unchecked or uncheck it --> --> you may need to reload the file into the texture file blank with the "..." button --> save the model and try again... Still problem go to 2.

2) Open the .mdl in med --> go to skin manager --> go to skin settings--> go to texture file --> click export texture... Can't export go to 4.

3) Export skin to .pcx. --> In the texture file blank click the "..." button and load your new saved .pcx file. --> make sure "exturn" is unchecked --> close the texture file slot --> open texture format slot --> makes sure 24 bit is checked --> makes sure mipmaps are checked --> uncheck alpha --> click "ok" if you can. exit skin manager --> save .mdl file.

4) You need to modify the pcx file in gimp and reload it into the .mdl file with "exturn" unchecked.