Jase, three words for you: portable network graphics (PNG).
Maybe it was Front Page that converted them, but those pictures in .jpg format are 5 to 10 times more bytes than they need to be, and not as clear. This is particularly so for the CD Doctor graph, which I know started out life as a perfectly sharp 6-7 kByte .png file (as compared to the blurry around the edges 61 kByte .jpg version). While JPEG is great for photographs, PNG (and even GIF) are usually better for screen shots with their sharp edges and large runs of constant color.
Of course, I don't really mind if you prefer to use JPEG, but PNG or GIF will save you web hosting space and bandwidth transfer fees (if you have to pay at that level).