Re-sampling: Let's say you are working in Adobe Photoshop and you have a 72dpi image. If you re-sample that image by replacing "72" with "300" in the Photoshop's Image Size window, you would just re-sampling neighboring pixels to add more pixels per inch. It gives a slightly softer result, though does not drastically improve the appearance. The result will be generally blurry and pixelated depending on the degree of re-sampling.
Scaling: In Photoshop this can be found under image and image size, the document size is the place you should be focused on. You've started with an image that is 300dpi at 2 inches square and made the image bigger in your layout to fill the CD cover. Although the image was in fact 300dpi, when you enlarge it the resolution decreases. So, your image that was 300dpi at 2 inches is only going to be about 120dpi when scaled up to 4.75 inches. This can result in more jagged appearance depending on how large you scale the image.
