Although I would also agree that you should rather be using a dedicated GPU to run Most Wanted, if your friend with the same specs got it working, then maybe you just need to update the drivers? check Intel's site for generic or your motherboard maker and see if you have the latest drivers.
hey if you are able to run assassin's creed it will be running at lower settings only it's your luck and by the way for most wanted either update your drivers or go for any other game like carbon or burnout paradise it will run good on that igp...as my friend having the same igp was playing it.
Definately, the graphic card is the real solution for games if you are tight on budget just spend an 50$ and you will get hd 4650..it's the best cards for moderate gamers.
With hd 4650 you can play every game on high setting on the 1280x768 resolution.Even the latest games like bad company 2 etc will work fine on high settings.