Corrupt excel .XLSX file?

Hey guys,
i have a couple of excel .XLSX files that i have been trying to open but i haven't had any luck with then excel says "excel cannot open filename.xlsx because the file format or file extension is not valid. verify that the file has not been corrupted and that the file extension matches the format of the file"
i have download the compatibility pack for office 2007 and tried to repair and extract the data from the file using the excel programs but i get a message that says the file is corrupt and cannot extract or repair the file.
i have tried this on all the files and selected every option i can in the repair menu, but i haven't had any luck with it.
is there a way to repair the file or am i going to loose the data stored in these files

Any and all help will be greatly appreciated

I tried different software pkgs to recover the excel file and these are the errors generated:

eRepair Excel is an advanced Excel repair tool, which is able to fix Excel files of any version (xlsx repair also supported), except for password protected files. Excel file repair toolretrieves the contents of the damaged Excel file and saves the recovered data as a new workbook, while the source Excel file remains unaffected.

For more information: http://excel.erepairtools.com/

If doesn't help, look here: http://www.filerepairforum.com/forum/microsoft/microsoft-aa/excel/935-excel-repair-error-detail

MS Excel File can get corrupted due to virus attack, missing MS office files, power failure and other possible reason that can be fixed by only use any third party Excel Recovery which can easily fix any kinds of error and corruption use any repair tool to fix your problem instantly.

You may try its free demo version first.

Download:- http://www.softmagnat.com/excel-recovery.html

I advice more advance or professional Excel Repair Tool which can easily recover of both XLS and XLSX files of MS Excel and capable to recover all kinds of information embedded in the Excel sheet like text, hyperlinks, objects, graphs, OLE objects, etc.

To get an idea on how to resolve this issue visit: http://www.mannatsoftware.com/stellar-phoenix-excel-repair.html