HELP please T_T REZ editing non photoshop

OK I've been trying to edit a texture for almost a week now and i suck -.-, I'm doing the non photshop version. My only problem now is when i save the image and import it i get this message. Right after i save it when im in the importing part it says " unable to laod tga file....make sure it is an uncompressed 24-bit or 32-bit image." I'm using gimp to edit the gun and i found a post in another forum saying "untick the box that says RLE compression when u save the image", but when i save it there are no boxes? or RLE?

If anyone can help me with this THANK YOU VERY MUCH T_T

GIMP are teh failz. Just get a photoshop portable version.