i have been trying to play a few different games but cannot… i have a laptop (hp pavilion zv5000)?

i just upgraded my ram from a 256mb to a 1g which made the computer faster a better but i still cannot play the games… from what it looks to me it is the graphics… one game is just a small hunting game… i can download and play but the animals dont look like animals, they look more blocky all the way around them… also eventualy it will just crash on me…. another game downloads but when it gets to the games menue option, it as well is very blocky where the letters would be. i can still click on an option from the menue but right away it crashes…
i have seen other answers to this kind of question and it doesnt look as though i can change my graphics card if that is even the problem… if you know of anything i can do so i can play my games please help… my graphics card is a GeForce4 420 Go 32m