I have just bought a VGA canble and sound lead to

I hook an HP to a Samsung HDTV in much the same way. Two things, if you connect to the monitor out on the laptop after it's already started up with Windows loaded, you will need to do a restart to activate the monitor out. You can leave TV on during this process. Second, be sure you have selected the correct input source on the TV. Mine actually has a PC input and that's how it reads when I select it via the TV's remote.

Something I've done since that you may want to consider is upgrading to a graphics card (via PCMCIA card or if daring enough you could try upgrading the internal mini-PCIe graphics assuming your PC is capable of that) that support DVI or HDMI out. This method is better if you intend to connect through a home theater or surround amp.