Open skin1/customer/main/product.pl
{include file="dialog.tpl" title=$product.productcode content=$smarty.capture.dialog extra="width=100%"}
(I believe this is the code, I'm trying to remember off the top of my head, if not then .productcode is not correct but just replace what's there.)
{include file="dialog.tpl" title=$product.product content=$smarty.capture.dialog extra="width=100%"}
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