65,00 empty rows

I'm running Excel 2003 under Win 7 Pro x64. I'm doing a spreadsheet with about 700 rows -- but the worksheet is 65,035 rows long.

I have tried selecting from line 700 to the end and deleting rows, but that only makes the row numbers flicker.

I have tried selecting the active rows to copy them to a new spreadsheet, but I can't highlight all the rows.

I also note that the merge and center button is greyed out on this file, but not others, so I guess this file is corrupted somehow.

How do I get out of this mess? Save as .CSV and re-enter? (But then will that save only the relevant rows?) Copy the 700 active rows a few at a time to a new spreadsheet?