An external HDD is very easy to setup and use. It's invaluable for backing up those precious music and picture files, as well as your Windows configuration.
First things first: Does your Laptop have a USB port (most do) ?
If yes, then it's really down to the size of drive you want.... A few ideas:
To setup the drive, you simply plug in the usb cable to your laptop, then plug in the mains adaptor and switch on.
Windows should recognise the drive, and you can format it (more on this later) if required, although most come ready to go.
Once recognised, you can simply use it as you would the drive on your laptop....Create folders, drag your pictures, music and documents over to the new device.
That's the basics! The site I posted is a tried and tested one used by many here, but there are plenty of other suppliers around.