I ordered a Samsung Q430 a while ago and i was wondering if it could run JUST CAUSE 2 on like medium settings. It has a GeForce 310m graphics card (512mb), Intel Core i5 460M, 4 GB of Memory, and 500 GB Hard Drive.
It would be my guess you'd better be prepared to use low graphics settings to get fluid game play.
Here is a video of a Geforce 310M playing JC2 on low graphics settings @ 800x600 resolution. And even without action you'll see the FPS dip below 30FPS. Full graphics setting options shown at the end. Lots of 'eye-candy' stuff turned off. http://www.vidbite.com/play.php?vid=7026
Almost any new game - Fallout New Vegas, Just Cause 2, Call of Duty Black Ops, Call of Duty Modern Warfare 2... etc will require Steam to run. It is a support application that allows you to play your games on any computer with the internet and play them without the disks.
Your laptop will *not* be able to run Just Cause 2. It is a very power-hungry application (processor and graphics wise), and the 310- is not a good card. NoteBookCheck is a very useful site for checking these kinds of things.
I would recommend building a desktop PC (cost me $890AUD including case, monitor and keyboard/mouse bundles) that can handle most games on [HIGH] settings; only use your laptop when you are out and about and need a computer for low-power tasks like document processing and web browsing.