File Format Error
 

When I try to open a .xls file it show the error " The File you are trying
to open ps.xls 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 want to open the file now ?"

When I click on Yes it opens the file without any issues.

Question. Why does it show this error when the Excel 97- 2003 is supported
by Excel 2007. Is ther any way to supress this error?