The purpose of the Print Preview is to display as exactly as possible what the final, printed output will look like. This is so that you can easily perfect (customize) the printed output before you actually have to print it.
Take a look at the Print Preview: press <Ctrl-P>; make sure that the 'Force to One Page' option is not selected; press 'v' (or click on the Preview button).
Depending on the size and orientation of the paper selected (per File, Page Setup and/or File, Printer Setup), and the width of the spreadsheet area plus the task bar area, you may see two or more pages in the preview. If you see up to four pages in the Preview, go back to the Print form and select the 'Force to One Page' feature. (To return to the Print form quickly from the Print Preview in Time Line for Windows, just press the letter 'o' or click on the Options button.)