Jim,
Do you have the manual for this register? In the section titled "Getting Started" there is a procedure for initializing the register. This clears all of the information from the previous owner and returns the register to an 'out of the box' condition. If you don't have the manual, you can download one free here:
http://www.sharpusa.com/CustomerSupport/ProductDownloads.aspx
Select "model not listed" and enter your model number. Be sure to capitalize the 'XE' and 'A', the stupid Sharp web site is case sensitive.
Hope this helps ...
Steve, July 2010