OpenGL thing, please help!

[nightyday]

I've been trying to play Fire Emblem: Path of Radiance, but every time I choose to play it give me this message:

Can't create opengl renderer. You might be missing some required opengl extensions, check log for more.

Then Dolphin stops working, and I have to close the program

This is the first time I'm using Dolphin, so what's the problem, and what's a OpenGl anyway?

Also every time I open Dolphin, it gives me this message:

Failed to load Plugins\Plugin_VideoDX9.dll - unknown error.


PLEASE SOMEONE HELP!!!

Thankyou