Hi,
I've created a file in excel 2007 with extension(.xlsx) several days ago. i
was able to open and save the file then. However, when i tried opening this
file yesterday, it prompts me this error message: Excel cannot open the file
'2007.xlsx' because the file format or file extension is not valid".
Therefore, i was not able to open this file.

This shouldn't have happen as i've tried creating and save another document
in excel 2007. The file extension was also .xlsx and i can opened the
document.

Please advise what can i do to retrieve back my file. It is a very important
file.

Thanks,
amylim