How to use an Excel 1997 files with line chart that have date & ti

I have many old Excel 1997 files with line graphs that show up the x axis
date and time values. The old Excel 97 show about ever 10 or 20th date/time
stamp in the x axis, but the new 2003 show only black spots at the bottom of
the line graphs.
How do I get Excel 2003 to produce a line graph to show time/scale data that
has dates and times like the old Excel 97 did?