This is also happening to me. It's very unfortunate, but the game is unplayable as it is. I don't mean to be rude, but it's just too annoying to tolerate.
Everything just freezes for a split second when the following sounds play:
a) Horatio's footsteps
b) Main menu, hover-on and hover-off of a button
c) Probably others
I also tried everything I could try (every possible combination) in winsetup.exe. Windowed, antialias, nearest neighbor, every combination of sound/music drivers, all the checkboxes. I do mean everything. Also DD/D3D. Buffer size to all possible sizes. Nothing helps. I also tried running the game with administrator permission. I even tried disabling Steam Community for the game (so the overlay doesn't pop up).
Steam Version
Win7 64 bits
4 GB RAM
GTX 260
Core 2 Duo E7200