When you double click on an Excel workbook (.xlsx or .xls), the following message appears.
In versions of Excel pre-2007, you could fix this by editing the Open options in the WIndows Explorer, disabling DDE and adding the “%1” at the end of the command path. This is not available in Vista. However, it is not built in to the Excel Options. Open up Excel Options.
Go to Advanced, then the General section and remove the check on “Ignore other applications that use Dynamic Data Exchange (DDE)”