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Cannot open html file with .xls file extension in Excel 2007

Medium Priority
Last Modified: 2012-05-07
When opening a file (with .xls file extension) in my web browser (IE6), it delivers an error "because the file format or file extension is not valid" msg.  When the file is saved, it can be opened in Excel '03, but not Excel '07.  I need for clients to be able to view in Excel '07.  What is causing this error, and how can it be fixed? NOTE: Changing the filename to .xlsx does not help.  File attached.
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Please attach file,




Thought I did it.  I cannot upload the xls file in question because part of the problem is it isn't even being recognized as a .xls file (evern though Excel 2003 can open it).  When I try to upload the file to this site (from my computer which has Excel 2007) it fails giving the error...The extension of one or more files in the archive is not in the list of allowed extensions: [Content_Types].xml

Again the hyperlink to the file online (sorry but authentication required/password protected) so I can't put the link up.

Does this problem shed any clues as to what the problem might be?


Again the hyperlink to the file online (sorry but authentication required/password protected so I can't put the link up) opens with Excel 2003.  
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Hi, I encounter similar problem, a message "The file you are trying to open, "<Filename>", is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you wan to open the file now?"

The error number is 101786.

After clicking YES, the file can be opened though. But would like to know how to by-pass this message.
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