My wife's laptop developed arthritis over the last couple of months. I dinked around a couple of times trying to get the kinks out, and it sort of got better some of the time. The last straw was when the audio started stuttering. I spent the better part of the day tracking this one down. Learned a couple of things on the way, like how the prefetch directory accumulates stuff over time and can slow your boot time to abysmal*.
The stuttering audio problem was caused by a value getting changed in the registry. This particular value tells the hard disk driver whether to use PIO (Parallel Input/Output) or DMA (Direct Memory Access) to transfer data to and from the hard disk. DMA has been the way to go since hard disks had hydraulic actuators. The only reason for using PIO would be because you worship Satan and you like to suffer, maybe?
Anyway, after much poking around I finally found these two pages:
Regedit to go in poke at the registry myself, but then there was a little confusion over just which entry needed to be changed, so I downloaded the magic program and ran it and it seems to have fixed the problem.
There is one thing still bugging me and that is how this setting got changed in the first place. Was it malicious, or was it someone's programming error? I don't think it's random, I mean it is common enough that someone took the trouble to create a solution, and the solution is very specific.
The other thing that is weird is that none of malware detectors I ran (anti-virus, Ad-Aware, Spybot Search & Destroy) found anything wrong.
*Windows Prefetch directory is controlled by this registry key:
Set it to 2 to include system files only and exclude applications.
Session Manager\Memory Management\PrefetchParameters\