Played some more on my laptop. Still no lagging. Amazing.
However, I don't want to play on my laptop, I want to play on my stationary and it annoys me that I can't figure out why it lags.
My stationary has a faster CPU than my laptop.
My stationary has a shitty Radeon HD 5450 GPU (I'm not a PC gamer), but my laptop has onboard graphics, which ought to be even shittier.