FSX Texture Downsize

Hi there fellow simmers! If you check my specs you can see i have a rather indecent Rig for fsx (a laptop with an ATI card (!))

So I have embarked on a quest for lightest FSX possible.

I am currently tacklin' 2 hogs: Carenado C208 Grand Caravan and PMDG JetStream J41.

All i want is to make the textures (outside and Virtual cockpit) more FPS-friendly. Truth is, I do not have any texture-managing knowledge.

How should I start? Anybody can hand over some clues?

I'm also looking for some light clouds, but that should go in another thread, maybe.

Any help is appreciated.

Thank you and have happy flying!

Nicolás