OK, so I assume you are trying to fix pages like this one:
http://www.wildshopping.com/customer/product.php?productid=23&cat=3&page=1&XCARTSESSID= 7d9a0574f0300dfc527441d8f506a88e
If you've already made the changes I described in my first post, then here's what to do...
In an image editor, scale your screen-shot image down to a reasonable preview size.
Then log into your admin area.
Go to "Modify Product".
Enter the product number, and click "search".
Select the product and click "Modify".
In the "product thumbnail" section click "change image".
Under the heading " File on your local computer", click browse.
(This process may differ a bit depending upon your version of x-cart.)
Select the file of the new preview image on your hard drive.
And click "Open".
Then click "Apply".
Then click "Submit Changes".
At this point, your page will look a lot better because you'll have a small preview image instead of the big one. It'll also load faster.
Next, go back to the modify product screen for the same product.
Scroll down to the "Detailed images" section.
Click Browse and select the file of the high resolution image on your hard drive. (The original large screen-shot.)
In the "Alternative text" field, enter "Click to Zoom".
Then everything will look the way you want it.