Firstly, you're attempting to do things the hard way. While it's possible to download pictures directly from your camera (as you're trying to do), it's far simpler to use an SD card reader, such as this one:
http://www.ebuyer.com/product/132044
(They're widely available. Try Asda or Tesco. I've even seen them sold for �1 in a 'pound shop').
Using a card reader (which plugs into a USB port), you simply plug in the SD card and then access the files, on your PC, in exactly the same way as if they're on your hard drive. (The card reader appears as an extra drive. You simply double-click on its icon the view the contents and to copy the files to your hard drive).
However, returning to your current attempts to download images directly from your camera, you usually need to install software (which comes with the camera) to enable you to do this. It's possible that the software might not be compatible with Vista. (As you state, it's also possible that you might need a driver but, given users of earlier versions of Windows don't require a driver, that would seem to be unlikely).
When downloading directly from a camera, different manufacturers may specify slightly different instructions but you always need to have the camera switched on (with the card in place). Some cameras require that you have to select a 'download' setting, on the camera itself, in order to get things to work.
As I've stated though, using a card reader is far easier. They cost next to nothing and you can forget all about drivers and software compatibility.
Chris