it first looks in the registry to see if it has a defined application
for that extension. if not it looks at the first 8 bytes in the file
and recognizes it as biff8. (excel97-2003)


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keepITcool
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Zoo wrote in

I'm using Excel2002 on Windows2000.
I had a book whose name is a.xls.
And I changed its name to a.ddd in order not to start Excel.exe by
double clicking the file.
But double-clicking the file, Excel.exe starts.
How does Windows recognize the file as Excel's data file?