I would suspect that the other files have remained in the XL97 - 2003 format
(*.xls), where the other has upgraded itself to the XL2007 format (*.xlsx),
you should open the file in XL2007 and save as a 97 -2003 format and all
should be ok

--
HTH
Nick Hodge
Microsoft MVP - Excel
Southampton, England
www.nickhodge.co.uk
HIS


"elusiverunner" wrote in message
...
One of my Excel worksheets is no longer recognised by Excel 2003. I have
about a dozen worksheets that I use a work [using Excel 2003] and take
them
home to work on there [Excel 2007 Beta].

All but one are accessible on both Excel 2003 and Excel 2007. When trying
to use the worksheet on Excel 2003, where it was originally created I get
the
message "The file is not in a recognizable format". However, when opening
the file in Excel 2007 Beta the file is still accessible.

Can I get some assistance on what is happening here as I would have
thought
if the 11 other files can be accessed by both programs then so should the
one
I am having difficulty with.