laggy on good comp, but doesnt lag at all on rubbish laptop

I'm not sure whats wrong with my comp, it keep lagging for some reason when i try to watch a movie or some video. But it doesnt lag at all on my rubbish laptop. It started about a week or 2 ago, is there a way to fix that.

Main Comp
http://i44.tinypic.com/acvd74.png
http://i44.tinypic.com/1zlrbso.png

rubbish laptop
http://i39.tinypic.com/24zzr79.png
http://i40.tinypic.com/vzcxzq.png

I usually have a few programs open like always and it doesnt lag at all, and i play 2 games at once and watch some vid.

But now its just ms and the vid and the vid is laggy ( it finished loading the whole thing but when I watch it, it lag like walking in ch 1 fm on rubbish comp)

I even try different vid ( just incase only that one lag) but all of them are like that..so I guess there's something wrong with my comp.