I have recently bought a new laptop, an ASUS N56VJ-S4149H. I bought it to use it in all possible ways I could want, so that would be gaming downloading and streaming movies browsing the web and programming software. So far it has been running great but one thing annoys me a little bit.

I frequently play Mount&Blade: Warband, it's a great game and you should check it out. Everything runs smoothly but only when I turn down the 'Texture Detail'. Otherwise it will lag a lot and I can't really play. Now my question is: Is this a problem of not enough RAM? At first I was really sure it was but after thinking about for a while I'm not anymore. My computer only has 4 Gigabytes of RAM and there is still a slot open. So will it improve when I buy another 8 Gigabytes?

EDIT: It has an Nvidia GeForce GT 635M inside. and an Intel Core i5 3230M CPU with 2,6 GHz.

Help and answers are really appreciated.

Thanks to all.