Unable to open excel file directly in Excel 2013

Hi, I uninstalled my previous version of MS Office (2010) and installed MsOffice 2013.
Now I am not able to open excel files directly by double clicking on the file.
It opens only the excel application but not the file. However i can open any excel file through open command in the excel application.
Please help.

I tried using the following options

Tools|Options|General|Ignore other applications (uncheck it) - Doesnt Work

--- or ---

Close Excel and
Windows Start Button|Run
excel /unregserver -Error Message
then
Windows Start Button|Run Doesnt Work
excel /regserver

The /unregserver & /regserver stuff resets the windows registry to excel's
factory defaults.