Ayuda con slideshow

[Luciata]

Tengo este slide show de imagenes. Quiero que al hacer click en cada imagen se amplie. Como lo haaaago'?¿

Código HTML:

<script language="JavaScript">
// Browser Slide-Show script.
// With image cross fade effect for those browsers that support it.
var slideCache = new Array();
function RunSlideShow(pictureName,imageFiles,displaySecs)
{
var imageSeparator = imageFiles.indexOf(";");
var nextImage = imageFiles.substring(0,imageSeparator);
if (document.all)
{
document.getElementById(pictureName).style.filter="blendTrans(duration=2)";
document.getElementById(pictureName).filters.blendTrans.Apply();

}
document.getElementById(pictureName).src = nextImage;
if (document.all)
{
document.getElementById(pictureName).filters.blendTrans.Play();
}
var futureImages= imageFiles.substring(imageSeparator+1,imageFiles.length)
+ ';' + nextImage;
setTimeout("RunSlideShow('"+pictureName+"','"+futureImages+"',"+displaySecs+")",
displaySecs*800);
// Cache the next image to improve performance.
imageSeparator = futureImages.indexOf(";");
nextImage = futureImages.substring(0,imageSeparator);
if (slideCache[nextImage] == null) {
slideCache[nextImage] = new Image;
slideCache[nextImage].src = nextImage;
}
}
</script>


<img border="1" src="images/1.jpg" width="550" height="245" id="Fotos">
<script language="JavaScript">
RunSlideShow("Fotos","images/1.jpg;images/2.jpg;images/3.jpg;images/4.jpg;"
+ "images/2.jpg",5);
</script>