File getting corrupted and not able to open - Serious problem ??

[Mahesh]

I have a Office 2003 xls file which I opened in version 2007. Used 'Convert'
option to convert in 2007 format and in the Review tab used 'Protect
Worksheet' option to protect it. After all was done, I clicked on the 'Yes'
button on the 'Do you want to save changes' dialog box and that's it. The
file is not opening now. I am getting a message that says - 'Excel can not
open the file xyz.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'.

It has destroyed two of my files already... Can someone please help? I have
some important data in those files that I must be able to retrieve...

Thanks in advance.
- M

 

[Mahesh]

I found that regardless of converting to 2007 format, even if I just create a
new file in 2007 and use 'Protect Worksheet' I can't open it after that at
all - What a protection !!

- M