Most of the failures with XLS file extensions and along with many of the other files are registry errors. Cleaning the registry most likely will fix a lot of the conflicts with XLS files.
XLS Problems? How would you like to proceed XLS files?
Scan Only XLS files:
Free XLS Scan
Repair Only XLS files:
Repair and Scan:
XLS Repair and Scan
XLS File Openers
XLS files have at least 2 methods(s) open/repair. The XLS applications which fix or use XLS file format include: Excel Worksheet, Works Spreadsheet
Fix XLS Errors Correct XLS Issues Scan for XLS Problems