I finally found a solution(at least on my machine: a laptop running windows XP, with a ||built-in sound card|| which is what seems to produce these errors)
I have installed patch 1.2 and 1.3.Set sound acceleration ( Start->Run->dxdiag ) Sound 1 and Sound 2 tabs each to 25%. (0%, 75%, 100% all produce double/repeating sound from my tests.)
Put in the CD and when the menu pops up, set the options under 3D Sound to: DirectSound3D Software Emulation, Reverb: None, Use Mp3 checked.
This solved all my (annoying!) sound issues and now I can play MM9 without getting a headache from the sounds lagging/repeating! I hope it may help others.