Performance drop after installing new drivers

Hello everyone, hope ya'll are doing well! 

Here's the thing. I got a laptop replacing my shitty shitty old computer, and i am pleased with it so far.  I am not a gamer, very casual one anyway, i don't pixel peep, and don't need a high end gaming rig. So i got modern warfare 3, and at first i was blown away how good the game plays at 1080p on high setting, using fraps i got got steady frame rates between 30-40fps.  After i realized i didn't have the latest drivers, so i updated the graphic driver with a clean install. And now i'm regretting it. Now pretty much no matter what settings i play in, i can't get more then 23-24 fps. I even installed the old drivers, but didn't help.

At first i thought it might be the game got more demanding after a few levels, but even at low settings and 800x600 resolution, i can't get more then 27-28 fps. So any ideas, tips? Any of you had similar issues?

Btw, i have a Lenovo z50-70, i3-4030u, nvidia 840m 2gb ddr3, and 4 gigs of ram.

*deep sigh* *facepalm* It appears as though the problem was so silly, i'm, embarrassed. I set the power plan to power saver. Now that i set it back to high performance, everything is working like before. Never had a laptop before, so i never use to fiddle around with it.

Its aright. Most of us had that "new laptop issue" before. They just take time to fiddle with until you fully understand it. It's like trying to mod an Xbox one when your Used to the 360's.