Hi,
What you will need to do is follow this link and download a trial version of Corel Office http://www.corel.com/servlet/Satellite/us/en/Product/1207676528492#tabview=tab1
Once downlaoded you will need to open the Quattro Pro x4 trial and then open your files one by one then choose file then save as and save them into the Works spreadsheet format.
Once they are all saved in works format youcan then remove the X4 trial from your machine and all you files will be converted so you can use them
Let us know if you need more info
Thanks
IEEE Network Engineer, Microsoft
approx 20 years of experience from software to hardware design