We have migrated a client from sharepoint 2003 to sharepoint 2013. But when they open a file from sharepoint, the browser puts a ms-excel:ofv|u| in front of the url and then the file does not open. It happens with MS word files as well. The client has Office 2010 on their machines. Please help me solve this?
This is actually a somewhat known issue and it's not due to the migration. What I would ask is, do your clients have some component of Office 2013 installed?
Usually what happens is that when a stand-alone Office app like Project 2013, Lync, or Visio 2013 is installed after the main Office 2010 suite the 2013 program changes the protocol handler so that the Office 2010 programs no longer understand how to open the URL.
What you need to do to correct this is go into Programs and Features and locate the Office 2013 application and select "change" then go in and disable the SharePoint integration.
Here is a TechNet blog post with some screen shots: