Is this the error you are getting?
This file is not in a recognizable format.
If you know the file is from another program which is incompatible with Microsoft Office EXCEL, click Cancel, then open this file in its original application. If you want to open the file later in Microsoft Office Excel, save it in a format that is compatible, such as text format. If you suspect the file is damaged, click Help for more information about solving the problem. If you still want to see what text is contained in the field, click OK. Then click Finish in the Text Import Wizard.
If it is it is simply a corrupted installation of the compatibility patch. Uninstall “Compatibility Pack for the 2007 Office system”
Reboot your machine
re-download the compatibility pack from here
Reinstall and you should be good to go!