Originally Posted by Sleepy Hollow

It's likely due to the file size being too large. Use some kind of editing software to decrease the file size (or, if your email provides the option to resize photos for sending, you can use that, email it to yourself in a smaller size, then save to your computer).

ETA: another option, if you use facebook, is to load the photo onto facebook and then download the photo again to your computer. Facebook shrinks the file size when you post there.