Thsi msg occured when I try to paste one worksheet to another using excel97. When I try to use excel XP, it doesn't give me this problem.
In Excel 2000 and 2002 (XP) the number of Custom number formats is Limited by available memory.
Not sure what it is for Excel 97, but if you type "Excel specifications and limits" into the help it should tell you.
All-in-all it will mean you will need to delete some.:(