How do you switch between DX9 and DX10 in Crysis?

[mfh6375]

I can't find the option anywhere. Am I missing something? I have E8500, 9800 GTX, 4gb DDR2 PC8500 and Vista Ultimate 64. I get decent performance, but I wanted to see if DX9 would give some improvement.

 

[AzN]

You right click instead of double clicking crysis icon. It has the option for dx9