Script for Inno Setup to detect if the wanted version and build of VC Redist C++ is installed as explained: https://stackoverflow.com/a/8552775/2062444

vcredistversion.iss

[Code]
function IsX64: boolean;
begin
	Result := Is64BitInstallMode and (ProcessorArchitecture = paX64);
end;

procedure Explode(var Dest: TArrayOfString; Text: String; Separator: String);
var
  i, p: Integer;
begin
  i := 0;
  repeat
    SetArrayLength(Dest, i+1);
    p := Pos(Separator,Text);
    if p > 0 then begin
      Dest[i] := Copy(Text, 1, p-1);
      Text := Copy(Text, p + Length(Separator), Length(Text));
      i := i + 1;
    end else begin
      Dest[i] := Text;
      Text := '';
    end;
  until Length(Text)=0;
end;

function IsVcRedistInstalled(version: String; build: cardinal): boolean;
var
  regBuildNumber: cardinal;
  regKey: String;
  regInstalled: cardinal;
  regStringBuildNumber: String;
  strArrayBuildNumber: TArrayOfString;
begin
  Log('Check for VC Redist ' + version + ' with build ' + IntToStr(build));
  if(IsX64()) then begin
    regKey := 'SOFTWARE\WOW6432Node\Microsoft\VisualStudio\'+ version +'\VC\Runtimes\x64';
  end else begin
    regKey := 'SOFTWARE\Microsoft\VisualStudio\'+ version +'\VC\Runtimes\x86';
  end;
  RegQueryDWordValue(HKLM, regKey, 'Installed', regInstalled);
   //Normal version installed, compare buildNumber
  if(regInstalled = 1) then begin
    Log('VC Redist ' + version + ' Installed');
    RegQueryDWordValue(HKLM, regKey, 'Bld', regBuildNumber);
    Result:= (regBuildNumber >= build);
    Log('Detected VC Redist Build ' + IntToStr(regBuildNumber));
    Exit;
  end;
    Log('VC Redist ' + version + ' not in default directory registry.')

  //Check developer version
  if(IsX64()) then begin
    regKey := 'SOFTWARE\Wow6432Node\Microsoft\DevDiv\vc\Servicing\'+ version +'\RuntimeAdditional';
  end else begin
    regKey := 'SOFTWARE\Microsoft\DevDiv\vc\Servicing\'+ version +'\VC\RuntimeAdditional\x86';
  end;
  RegQueryDWordValue(HKLM, regKey, 'Install', regInstalled);
  if(regInstalled <> 1) then begin
    Result := false;
    Exit;
  end;

  RegQueryStringValue(HKLM, regKey, 'Version', regStringBuildNumber);
  Explode(strArrayBuildNumber, regStringBuildNumber, '.');
  regBuildNumber := StrToInt(strArrayBuildNumber[2]);
  Result:= (regBuildNumber >= build);  
end;