I solved my problem with PlanetSide. I use(d) some tweaking programs to optimize Windows. It seems that one of those programs changed a setting in the registry called "LargeSystemCache". The default value should be "0", but in my case it was set to "1". I changed it back to "0" and no more lag spikes. On high details (all set to high and all textures enabled) in large battles I get 75 - 130 FPS. The are still the high B/s peaks, but they're not affecting my FPS anymore.
Back to topic, I voted for Friday. A day during the week will be more difficult, due to work. But I'll see what the outcome of the vote will be.