Can i upgrade this computer?

I want to put some more RAM in my computer,but i don't know how much to get. I currently have 2 GB and i have windows vista home edition. i have this computer: http://h10025.www1.hp.com/ewfrf/wc/product?cc=us&lc=en&dlc=en&product=3442974 and i want to get a new video card. Can you tell me if there is anything i can put in it to run like Fallout 3 and crap?