[SOLVED] My computer won't show 240 hz

[mattful]

Hi I just recently bough a 240 hz acer monitor for sale. After purchasing yesterday I realized that my computer doesn't have an HDMI port and uses the DVI method for my graphics card. I purchased an HDMI to DVI adapter last night to only still get 120 hz as my highest refresh setting. Why is this happening? I have the display port plugged in as well but I'm still stuck at 120 hz.

 

[ScrewySqrl]

leave it JUST display port

 

[Glenwing]

What graphics card?