GTX 680 Dual Monitor Windowed Game Lag

[StrongJoshua]

So I just got a 2nd monitor, specifically an Asus VG248 144Hz. This is my setup:

Asus Sabertooth z77
Intel i7 3770K
Evga GTX 680
Corsair 16 GB DDR3
Asus VG248 144Hz
Asus VE248H 60Hz


I'm attempting to run Team Fortress 2 in windowed mode on the 144Hz and Chrome on the 60Hz. The game runs at an average of 100FPS at high settings, but it lags as if I were playing at 20FPS... Why does windowed mode kill my GPU? Does that have to do with settings on the monitor or am I expecting too much of my 680?

 

[StrongJoshua]

Disable desktop composition in the game's compatibility to reduce lag.