This was the issue when I wanted to upload an xls file to my web application. With basically trying out everything, this was what solved my issue.

  • Download the 2007 database engine  from the link

  • Installed it on the application server.
  • Open IIS using inetmgr from the run prompt.
  • In application pool area, click set application pool defaults
  • A new window will pop up, find “enable 32 bit applications” and change it from false to true
  • Restart the application pool
  • Now try again to upload the file, the error message will surely disappear and you will be able to upload the file.