Cannot Associate XLS files with Office 2010 after upgrade from Office 2003

OS: Windows 7 Pro x64 / Windows XP Pro SP3 x86
After upgrading from Office 2003 to Office 2010 excel 2003 files (XLS) are no longer associated with office, it ask to browse to program to open.  
Have unsucessfully tried the following:
Method 1:
Control Panel -> Default Programs -> Associate a file type or protocol with a program -> .xls :
---> Change Program -> Browse (Check Always use the selected program to open this kind of file) -->
Browse to: C:\Program Files (x86)\Microsoft Office\Office14\EXCEL.EXE
-WILL NOT OPEN --OR-- Associate

Method 2:
Right Click on an .XLS file -> Open With -> Choose Default Program -> (Check Always use the selected program to open this kind of file) Browse -->
C:\Program Files (x86)\Microsoft Office\Office14\EXCEL.EXE
-WILL NOT OPEN --OR-- Associate

In the process of doing an office wide upgrade from Office 2003 to Office 2010, and have stopped the process because I have encountered this problem on more that 2 workstations (XP & 7).
Rebuilding the profile on one workstation fixed the problem, however their has to be a registry fix that can be applied to fix the problem.

Thanks in advance.