I assume you are running stock sounds. If nmot, then you are going to have to live with those pauses in Vista due to Vista replacing DirectSound with the standard Windows sound API and the added overhead of that API.
There is no hardware acceleration slider in Vista as there is no DirectSound support in Vista.
Sound is a real problem in Vista. Even Microsoft could not figure out a way for high speed streaming content to be played and allow the network connection to run without reducing the bandwidth available by 35%. Used to be 50% reduction, but they changed it to 35% in SP1.
And yes, it is not a good idea to be changing video or sound card drvers in Vista. Vista64 is worse in this regard. Of course, Vista64 has its own set of problems up and beyond the 32 bit version of Vista.