I currently use Photoshop CS5, but did have CS3 a couple of years ago. Adobe Bridge is a filing system for Photoshop CS and not for Elements. I have not heard of Adobe Photoshop Elements CS3- are you sure it is not plain Photoshop CS3? As I understand it DNG is an Adobe RAW file, and CR2 is the Canon version of RAW. I am not familiar with RAW, but maybe hssutton will see this and reply!
In the meantime have a read here: