i am using windows 8
i have installed worms armagedon and my monitor resolution is 1440*900
the game itself has a low fps when i run it with 800*600 resolution and when i change resolution to 1440*900 fps getsssss toooooooo low.
what should i do?

Install the latest 3.7.2.1 update (http://wa.team17.com/main.html?page=supp&area=upda&file=15).
Go into Settings -> Advanced settings, choose a Direct3D 9 graphics API from the drop-down list.
Restart the game.