Bad Screen Tearing

[temperzzz71]

So i just updated my cousins computer for Christmas and having really bad frame drops and "Screen tearing". I gave him my old GPU for his prebuilt computer. I have a I5 4400k, 8gb ram, and i gave him the GTX 750 ti SC. He has all the same specs except he has a I5 6600k. While using the card I played Rainbow 6 and had smooth 80 FPS the whole time. When trying it at his house today he would get 70 FPS then when looking side to side would drop down to 20 FPS. What is going on?

 

[temperzzz71]

MERGED QUESTION
Question from temperzzz71 : "Is it my Graphics card or something else"

I gave my old Graphics card to my couisn and he is having really bad screen tearing when looking side to side even on low settings. He has a I5 6600k and i have a i5 4400k and i had no problem with this card? What is the problem???