Computer Stuttering, please help!

[Daivat]

So my computer is fast enough (specs given below)
It used to work perfectly until yesterday i downloaded The Walking Dead season 2 from a piratebay. And i have quick heal anti virus 2014 with full protection on. And when i installed the game, it did not detect anything. (so probably not a virus)
Then when i ran the game, it started lag and it was stuttering. It did not come and go. It stayed continuously and it stuttered for less than a second. So i thought the game is lagging. So when i closed the game and found out my computer was doing this. I did open the task manager but did not find any weird process that would be causing this. Even after i restarted my pc this problem stayed. I removed the game and did a full pc scan and it said no threats detected. I'm very worried i have so much data on my pc and i dont wanna format the pc to get rid of this problem. Please help a community member

SPECS:-

-W7 ultimate

-Processor - Intel(R) Core(TM) i5-4430 CPU @ 3.00GHz, 3001 Mhz, 4 Core(s), 4 Logical Processor(s)

-Installed Physical Memory (RAM) - 16.0 GB

NVIDIA Virtual Audio Device (Wave Extensible) (WDM)

GeForce GTX 760

 

[Plusthinking Iq]

i blame the antivirus, maybe some other firewall protection "service" in conflict. end the conflict.

 

[simon12]

Don't download illegal software if you don't want issues and viruses (or anyway). Also note if you mention illegally downloaded software on this forum you could get banned.

 

[Dakshin]

Try buying the game and then installing