How do keep row height from changing? Excel 2003
 

I'm entering data in an Excel 2003 spreadsheet and it keeps automatically
changing the row height to that for two lines when the data entered clearly
fits on one line.

I've tried Autofit but it doesn't change the outcome, still sets it at
appropriate height for 2 lines.

It is getting really tedious having to change each row manually . . . and
then if data is later added or changed and the row height DOES need to be
wider, I'll have data cut off if I've manually set it too narrow.