excel 2003 slow when working with excel 2000 files
 

hello i have this problem when i receive excel 2000 files from a big customer
that work with office 2000
from last mount the files we receive become very slow to use
in office 2002 and 2003.
microsoft answer that i receive is that the customer have to upgrade...

still we need to use the excel files till they upgrade , we try to copy to a
new file but
it is still slow , viewer is not good for us.
any idea ..
thank you