EDIT: Sorry El Conejo... I see the 478 version is supposed to be easy to install using the original bracket. Not at all like the Zalman I was looking at...There almost has to be 4 square holes, indentations or ridges on the outer edges of the stock bracket where a stock Intel 478 cooler would grab onto with it's 4 plastic claws. Your new retainers should grab there as well. If not... It could be your computer was built to use a certain type of aftermarket CPU cooler? If that's the case... I found you a standard 478 bracket that should work...
http://cgi.ebay.com/Socket-478-Penti...QQcmdZViewItem