CPU Usage Spikes

[Exonerate]

So recently I've noticed while gaming, I'm getting spikes in CPU usage, which drops my framerate down drastically for a fraction of a second. Needless to say, this is not acceptable, since things will freeze for a moment, then teleport around. I've already tried Sysinternals' Process Explorer, but it doesn't really display anything using a lot of CPU except for the game itself, and DPCs occasionally (Which are apparently related to drivers?). So, G&C, how would I determine which process(es) are causing the spikes?