I tried to open a complicated Excel file today and Excel told me that it was corrupted and that it would try to rebuild it. Having tried to rebuild it, Excel reported the file was beyond repair. Now I have a backup somewhere, but I tried an experiment. I fired up the Open Office freeware clone of Excel (I think it is called Calc). It opened the Excel file that Excel itself could not open or rebuild. I re-saved the file using Open Office and now all is working fine and Excel can now read the worksheet again. The $0 clone succeeds where the $400 original fails.