Dandownunder,

You need to get something like "winmerge" and compare the old to the new, noting where you have made changes.

As Kim stated there have been major changes in the basics of the code as the old used tables and the new does not. So in the case of the product_info_display.php file, the old references the tables and their placement order. The new does not have these references to the tables.

There are other methods to move things around with the new ZenCart & css.