OK. I installed the newest version of iTunes on my PC so I could play with my new iPod. Instantly, all my video and audio started stuttering. It's made the PC useless for watching videos or using audio. Since I also use this machine to edit video and audio, this is a problem. Why do I know it's not the HDD? I can play the video and audio over my LAN just fine.
I also have the stuttering on streaming media, and when accessing media on other computers on my LAN.
I have three SATA-II drives, all configured correctly (I've tried all the suggestions on the stuttering problems...)
What else I have tried....
Updating audio and video drivers
Replacing all the Codecs
Deleting and reinstalling the video and audio cards
Tried the bare bones basic Windows Media player. Same problem. Even previewing the audio effects (the various beeps, books, and other noises Windows makes) stutters. "Boop" is often a rap sample "bobobo ooop ooop ooop op." Even the default Explorer "click" when clicking on a link is "clclclclclclclclikikikik" - it sounds like the page is redirecting 20 times!
I know for a fact this happened after installing iTunes - at first I thought iTunes had corrupted files when ripping - but this was not the case. I have the latest version of iTunes installed.