Shouldn't you be saving that file as personal.xlsb

http://www.rondebruin.nl/personal.htm
(from Ron de Bruin's site)

Marcela wrote:

the file you are trying to open, "Personal.xls", is in a different format
than specified by the file extension. Verify that the file is not corrupted
and is form a trusted source before opening the file. Do you want to open the
file now?? // will come up everytime new excel file is opened or xlsx file
type is open. recently reinstalled Office 2007 - it didn't fixed this issue -
any sugestions?

--

Dave Peterson