Random FPS drops with new high-end PC

I find I'm having more trouble running League smoothly on this new PC: i7 4790 3.6gHz MSI 970 GTX 4GB 16GB RAM 1TB WD HDD 7200RPM

Than on this one (HP laptop)(2011) :

i7 2630QM 2.0 Ghz 8GB RAM AMD RADEON 6770M 2GB 700GB HDD

Can someone tell me why? I have frequent FPS drops and trouble running smoothly in teamfights on my new PC than on my laptop. My laptop stays consistent at 60 FPS and i have NOTICEABLE drops in teamfights (as much as 20 fps drops) and sometimes randomly on my new PC. I'm still trying to figure this problem out.. invested so much money into this PC and didn't even get what I wanted out of it..