[ecfisa]

Hola Lepuke.

La sintáxis podes encontrarla aquí: ShellExecuteEx function

Un ejemplo de uso en Delphi:

Código Delphi [-]
...
implementation

uses ShellApi;

procedure OpenJPG(const aName: TFileName);
var
  ExecInfo: SHELLEXECUTEINFO;
begin
  ZeroMemory(@ExecInfo, SizeOf(SHELLEXECUTEINFO));
  ExecInfo.cbSize := SizeOf(SHELLEXECUTEINFO);
  ExecInfo.fMask  := SEE_MASK_NOCLOSEPROCESS;
  ExecInfo.Wnd    := 0;
  ExecInfo.lpVerb := 'open';
  ExecInfo.lpFile := PChar(aName);
 // pExecInfo.lpParameters := ...
  ExecInfo.nShow  := SW_SHOWNORMAL;
  if not ShellExecuteEx(@ExecInfo) then
    if GetLastError <= 32 then
      SysErrorMessage(GetLastError)
end;

// Uso:
procedure TForm1.Button1Click(Sender: TObject);
begin
  OpenJPG('C:\imagen.jpg');
end;

Saludos