The steps below have worked for me on Vista 64 and a few others have reported this has also worked for them. This may work for you, it might not.
1. Disable the following startup items (use CCleaner's Startup Items module for fast access or use MSCONFIG):
2. Disable the following Services (Note: When editing services, always access the services console by typing 'Services.msc' into the Run Command):
That's it. This should help with reducing stuttering. After making the changes above, I have had zero stuttering in-game and no audio playback issues (Windows Media Player). It should also be noted, for audio playback - disabling the use of Visualzations in your Audio player app can also reduce any stuttering.
Concerning Startup Items, one of the major tweaks you can perform to Vista or Windows 7 is by eliminating (disabling - don't delete them, lol) unecessary startup items. Some of these may include (depending if you have the relative software apps installed) the following:
PDVD8Serv.exe PowerDVD Remote Control - again, not necessary and will not effect remote control functions (at least none that I can find)
This is only a partial list. Everyone will have different startup items based on the applications installed on their system. Always use Google Search and research the startup item you are thinking of disabling. Make sure its not a critical component.
I also suggest using CCleaner's Clean & Registry functions on a regular basis. I usually run it every other day - takes moments to run and will remove lots of temp clutter.
NVIDIA Issue:
With the newer releases of the 186.xx series driver, NVIDIA's Stereo 3D Vision is installed by default. There is a known memory leak issue with this and a fix is supposed to make its way out. Personally, for me, I wont be using it so I haven't paid attention to this memory leak issue and its supposed update. It may be a non-issue with the 19x.xx drivers - I don't know. Best to uninstall it if you don't need it.
Remember, the steps I posted here are not a FIX but a work-around. I prefer to keep my system running well and do not need a facial recognition app (or any other unnecessary app/service) running on my system hogging resources.
That's it for now. Hope this helps some of the newer users out there who may be seeing the 'stuttering' issues described at the start of this post. If it hasn't helped you or you don't want to try it for whatever reason - well, all I can say is either return your system, sell it or accept it.
EDIT: Be sure to also see this post as it may help answer additional questions.