Enlarging thumbnails by clicking on them

[suavedesign]

I have a bunch (about 20)thumbnail jpg images that I want to enlarge to a much bigger image when you click on each thumbnail. But I dont want to have so many large jpgs on my website, because that will slow down the entire site.
Whats the best way to enable the user to view the thumbnail in large without making them into big jpg images?
I need the enlarged image to be as big as possible, because each one has text that I want the user to be able to read easily.
The link to my site is www.totalrecallsolutions.com
I dont want to make them into pdf's because not everyone has a pdf viewer, and I dont want to make them download it.
I also dont want to code each image onto its own webpage, even though I know that that will be able to be as big as I want, because I dont want to spend all that much time.
Any other options?
Thanks!

[lps]

How about parsing the picture to a div and set it to stretch to a bigger size. But this will probably mess up the resolution of the pictures.