Have you tried switching between OpenGL and DirectX modes?
Also make sure you've downloaded the absolute newest drivers from ATI/Nvidia, as the ones that filter through Windows Update are generally several months behind.
Currently, I get a PR of 3 with either mode (Windowed), but I've seen a few hardware/driver configurations that show big differences between OGL and DX.
Thanks for reminding me!
Now in OpenGL the Performance Rating is lower (between 1 and 6, but it sometimes raises and reaches 10) but the mouse is a bit laggy.
The framerate switches back and forth between 59, 60, and 61.
Thanks again, but I don't know which rendering mode I'll use!