Installing FSX aircraft

Can anyone explain why the outer paint doesn't show up on downloaded aircraft. I have tried several downloads and everything is fine except the skin. I know that it must be some kind of texture problem but I don't know how to solve it.A couple of the downloads were flawless and the paint is ok. For example the europa model worked just fine. The Swiss P-7 works ok mechanically but no skin color. Could this be a Vista thing?I'm running a Dell XPS 420 E6850 core Duo 3.0 with 3 gig 800 ddr ram and 8800 GTS 320 meg Video with Vista 32 bit system. Any advice would be appreciated.Blackie