Can I lower the game resolution?

[yuuko12]

I figure if I play the game at a low res like 320x240 I would get good fps. Atm I only get 20fps which is painful. In settings I can specify the window size but all that does is scale it.

By the way can my computer run Dolphin? I don't care about graphics all I want is the game to run smooth.
Intel Pentium 4 CPU 3.20GHz
2GB RAM, ATI Radeon X300/X550/X1050 Series graphics