For all those who got their hands on Virtualbox VMs provided by Oracle and not able to understand how to get the final vmdk file to import in VirtualBox, you can follow below steps:
a) Downlod the latest version of p7zip from http://sourceforge.net/projects/p7zip/
b) Extract the tar file using
tar -xvf p7zip_9.20.1_src_all.tar.bz2
c) Now go to the extracted folder and execute
> make > make install
d) Now go to the downloads folder where all .001, .002 –.007 files are present and use the below command to combine all the split files into one .7z file.
e) Finally execute the command to extract the vmdk file