{ ... }
if WaveOutGetNumDevs > 0 then
 ShowMessage('Wave-Device present')
else
 ShowMessage('No Wave-Device present');
{ ... }

function IsSoundCardInstalled: Boolean;
type
 SCFunc = function: UInt; stdcall;
var
 LibInst: LongInt;
 EntryPoint: SCFunc;
begin
 Result := False;
 LibInst := LoadLibrary(PChar('winmm.dll'));
 try
  if LibInst <> 0 then
  begin
  EntryPoint := GetProcAddress(LibInst, 'waveOutGetNumDevs');
  if (EntryPoint <> 0) then
  Result := True;
  end;
 finally
  if (LibInst <> 0) then
  FreeLibrary(LibInst);
 end;
end;