Debra Dalgleish has some notes and pictures at:
http://www.contextures.com/xlfaqApp.html#Unused

If hitting ctrl-End takes you way past what you think should be the last cell,
you'll want to check it out.

Sue

Excel often over-estimates the actual "used range" due to data being entered
then deleted.

Where does CTRL + END take you?

If far below and to the right of what you know is your real used range, go to
the row after the last row of real data then SHIFT + END + DownArrow to select
all rows below your data.

Now..........Edit>Delete>Entire Row(do not just clear contents, delete)

Do same for columns to the right of your data.

NOW IMPORTANT...Save the workbook.  Close and re-open to see changes.

Hit CTRL + END to see that the used range is what you set it for.

Gord Dibben Excel MVP