Hi!
First off what cable are you using, and what is the resolution of your monitor?
For 1080p 144Hz you will need DisplayPort, Dual-Link DVI, or HDMI 1.3 (or higher), while 1440p 144Hz requires either HDMI 2.0 or DisplayPort 1.2.
www.displayninja.com
Using the right cable your system should be capable of outputting 144hz. Bear in mind though its unlikely you will get anywhere near that at HD resolution or above in a modern even slightly demanding game. Your CPU and GPU are quite old at this point.