hi Viresh,

Download Cloudera 4.7 from this link http://www.cloudera.com/content/cloudera/en/downloads/quickstart_vms/cdh-4-7-x.html.

The file has an extension of 7z which can be extracted with 7zip (http://7zip.org/). Once the downloaded file is extracted, you can import the "vmdk" file into virtualbox or right click on "vmdk" file and select "open with Virtualbox".

Thanks