What model Sony Vaio is it? There's usually an on/off switch somewhere on the laptop, or it could a combination of the FN key + one of the function keys (F1, F2, F3, etc.).
If you look at the function keys, they should have symbols, and one of them might look like an antenna with signal waves or something, which would be your wireless on/off, if you don't have an actual switch anywhere on the laptop.