That will never work because:
Every folder with: gallery.xml, index.html, swfobject.js, viewer.swf and 2 folders: images and thumbs MUST be in a unique place, you can never have 2 .html pages or viewer.swf or whatever simpleviewer contains on the same level.
What you must do is the following:
Your root must ONLY contain:
Call the root: 'website' with:
Folder: images (images within the website generally)
sampleportfolio.html (is this the same as the index.html which contains the photos? If yes, you don't need it here, you can change the index.html in the folder 'sampleportfoliogallery' but then you need to adjust everything in the codes)
Folder: images (images for initail gallery - childrens books)
Folder: thumbs (thumbs for original gallery -childrens books)
Now: to display the gallery (which is in the folder sampleportfoliogallery) from the main page you put the following code in the main index.html:
<a href="website/sampleportfoliogallery/index.html"></a> That way, if you click the link to the gallery from the main page, it will display the whole gallery
You also can go and see how I've done it: www dot lingerieannemarie dot be, I used 3 times simpleviewer on the main page: Badmode, Lingerie and Nachtkledij, you can view the entire codes by looking at the source of the page.
Every button (3) has its own folder, with ONLY the content like above folder 'sampleportfoliogallery'