I didn't think there would be a reason for anyone to complain about the image...
On the CD, you have the raw image, which is 3000 x 2400 Pixels (Granted, its not the biggest you could get these days, but its still big enough to do almost anything you want without pixelization).
You also have a re-sized image for easier viewing on a computer, and thumbnails are also rendered.
If a customer is complaining about the size of the images on the CD, either they went to the wrong folder and are complaining about the re-sized images. Which seems silly considering the way the data on the CD's are presented. Actually, looking at a CD of a session I purchased, You have the Session Images at 3000 x 2400, then the Preview and Thumbs folder are all psd files, which you would need Photoshop to open. o.O Never noticed that before...