I stumbled in this post by chance.
Don't listen to the usual crowd of crows. YES! You can upgrade your laptop.
I know it for the simple fact I did it.
I have a MSi GT-660 which was bundled with a Intel i5-460M and an nVidia 460m.
I successfully upgraded my laptop to a i7-720qm* and a Nvidia GTX 675MX.
Though there are some discrepancies... you said you have a Nvidia 285M in a MSi GT-660, isn't it?
I'm working on my personal website in which I'll explain everything I did. I'm no professionist but I made a few photos of the procedure of my computer, before and after.
You must understand the this procedure is very very risky. You can lose the money of the card, damage your computer, start the third world war and trasmute your cat in a dog (or, if you prefer dogs, your dog in a cat (or, if you like them both, your dog in a deer, your cat in a mug)).
Jokes apart: you can but it's costly and risky. Is it worth? Sometimes.
What you have to understand is that the MSI gaming line IS created to be modded though by chance: the MXM slots has been created by the manufacturers not for let us expand our computers but for the computer care services to replace easily some pieces. By chance we are lucky since they invented the MXM module. The GT-660 (if we have the same model, I don't think so) have the MXM slot 3.0b which means that ANY card supporting the same version will work.
This is not an exact science: the manufacturer can apply some other software or hardware limitation (I have two old Acer with this problem) and it's all always very risky.
Also applying the card is a delicate procedure, not complicated (you need just a screwdriver and a good thermal grease) but you need to pay attention.
If you have any question let me know.
By the way now I'm looking how to overclock my i7-720qm, that's why I stumbled here.
* I know it's a crappy CPU, it cost me about 50$, a reasonable price for a jump in the void.