Setting default program for file types

Hopefully this is a no brainer for someone out there but I have not been able to get this to work right.  I have Office 2003 installed on base and I have created a layer for a standalone version of Excel 2007.  I want Excel 2003 to be the default Excel when opening xls files.  After importing the 2007 layer Excel 2007 is the default program.  I have tried playing around with layer prioritization setting the Normal priority and HKCR priority both really high and really low for the layer but Excel 2007 still wins.  If I repair Office 2003 Excel 2003 will become the default until I launch the Excel 2007 layer again than it wins.  Any help anyone can offer would be appreciated.