Converting Excel 2003 files to 2010

I recently changed from Office 2003 to 2010.  I have thousands of Excel files in the 2003 format.  When I open them now I’m saving them to the 2010 format, then I delete the old file.  This is time consuming, and I’m wondering if there’s a way to convert all files at once.  My Office 2010 is on a new computer, so I did a clean install, not an upgrade.  I’m still using my old computer with Office 2003, and I’d prefer not to upgrade that one to Office 2010.