Hello there. I have a problem with excel files and I am unable to find any solution

On my PC Office 2007 Professional installed. I have some excel files created in my old Office 2003. And when I am trying to load them in Office 2007, Excel shows me error window with the next message:"Excel has stopped working".
I copied corrupt files to my Laptop and they opened in mac office. So I saved them on the lap as .xlsx and tried to move it back on my PC. Some opened, but the most still do not.
Of course I tried to uninstall and install Office but no change. How can I get my files back?