This program allows you to open and see data from some corrupt Excel XLSX format spreadsheets that Excel 2002 and 2003 (with the Microsoft Office Compatibility Pack installed) and Excel 2007 and 2010 refuse to open. It allows you then to convert that data to CSV files for re-import into new Excel files.
This program works as a rudimentary viewer and editor of corrupt and healthy xlsx format files without needing Excel installed. With it you can view how Excel slightly skews its stored raw data in the background which is then transformed and rounded off for display in the program.
Version 2.0 adds a zip repair pre-treatment, increasing the chances of success. It adds an Alternatives menu which provides links to other free and freeware resources for Excel recovery as well as commercial solutions.
Also see my Excel Recovery Project here on Sourceforge. If successful, that program recovers formatting as well data whereas Corrupt XLSX Salvager only recovers data.