Link: Silent Development: Aerofoil 1.5.1 Released (64 and 32 bit builds available)
Requirements: Vista and Windows7.
Aerofoil is free.
One note: When you first run Aerofoil, your computer may pop up an error message about msvcp100.dll. In that case, you need the MS Visual C++ redistributable, which you can grab from Microsoft for free – both for x64 and for x86 systems.