DPC latency spikes = Help urgently needed *please*

I'm facing exactly the same problem on a Dell Latitude E6510. Same audio hiccups and latency issues as they seem to be indicated by DPC Latency Checker. I also tried upgrading BIOS and audio drivers (BIOS A04 and latest version of IDT 92HDxxx HD Audio Driver A16/6.10.0.6286 released 16/08/2010), to no avail.

Having done some further reading on the web, I am led to believe the latency spikes could be due to the RAID mode of the SATA controller, as default enabled by Dell (no idea why that would be useful by the way). Multiple sources seem to recommend switching to AHCI mode, but so far I did not succeed in that endeavour. See also http://forum.notebookreview.com/del...-switch-irrt-ahci-mode-e6400-e6500-vista.html.

I would seriously appreciate any further suggestions or support with switching to AHCI mode without re-installing the OS (Win 7).