I recently did some extensive tests on performance peaks and eventually reproduced something very similar on my home rig. Tried all kind of audio and video-card drivers combinations as well as disabling / enabling Windows services, the only thing I didn't touch is the BIOS which was already set up the way I want it.
The problem was solved reverting back to an older driver for the video-card - I have a Radeon HD 6570 and all 13.x drivers would yield the same result. Driver 12.10 brought performance back to normality, no more spikes.
I have a couple reports that using older drivers also solved the same issue with nVidia cards.
Not saying it will surely help those who posted here, but it is worth trying.