I have Excel workbooks that I have been using over a period of years.
Recently, I have encountered a problem opening the workbooks and get the
message that "the file is an unrecognizable format". If I open it in text
mode, it is not usable data. Files that have been just fine will suddenly
have this problem. I have backups but once excel refuses to open the
document, I get the same message trying to open the backups. I have emailed
the files to another computer and it still won't open. So it appears that
something is corrupting the files. Any ideas?