From personal experience as another relative newcomer I will tell you point blank that nothing worked until I did the .dll add from the MS website.  Without that, all the other stuff did nothing.
It wasn't like that for me. After building my new system, reformatting my C Drive, reinstalling Windows 7 Professional 64bit, then installing FSX & Acceleration followed by installing all my Captain Sim products, the sound in my 727 still had this issue.  got my sounds working normally by either reloading the aircraft or starting FSX by loading the 727 Cold-n-Dark (KSEA) or 727 Cleared for takeoff (KSEA) directly from the Documents\Flight Simulator X files and bypassing the FSX Start Menu.

I do have msvcr71.dll installed on my computer. It's in C:\Windows\SysWOW64\Msvcr71.dll. The file is dated Sunday, ‎8 ‎August ‎2010, ‏‎1:02:50 AM and Size: 340 KB (348,160 bytes) (Size on disk: 340 KB (348,160 bytes)).
That date is the same day that I reinstalled Window 7 on my new system. I never downloaded and installed the msvcr71.dll on my system.

Mark