Have you played any of the previous King's Bounty games on your laptop?
If not, you can try the King's Bounty - The Legend demo by going to this
page and see how that plays.
I'd set everything to minimum at first and then increase it if it isn't too slow.
If The Legend doesn't play well at minimum settings then you'll probably have a problem with Dark Side as well; however, if it plays okay, then you can give Dark Side a try since I'm pretty sure the same game engine has been used for 6 years now.
For reference I have a Quad-Core Q9550 2.83GHz with 8GB RAM. I've had this computer for 6 years now and I've only upgraded the video card twice and am now running it with an NVidia GeForce GTX 660 and it does great at maximum settings with all the King's Bounty games!
Good luck!
/C\/C\