For Excel 2010, to convert a decimal into a standard time format, enter the formula "=TEXT([desired cell number]/24, "h:mm")" and replace "[desired cell number]" with the correct cell number. This will change the number into a standard hours, minutes and seconds format.
To change the formatting in Excel 2003, first select the cell containing the number. Then click on "Format" and select "Cells" from the drop down menu. In the new window, click on the "Number" tab. In the "Category" box, click on "Time." A number of different formatting options will be displayed. Select the desired option and click "OK."