VirtualBox

i am facing a problem when i wanted to run the cloudera on the VirtualBox as well as the VMWare ! the problem is appearing in differentway in each of this platforms! in VMWare player after adding the proposed image of cloudera to the vmwareplayer, when i hit the run button in order to run the cloudera, it's just thinking a little bit and then jump out to the main page, where you have to choose the virtual machine that you wanted to use! in virtualBox the problem is appearing in a different way! when you wanted to create a new machine to add the proposed image of cloudera to it, thevirtualbox does not give you the the 64 bit option for the guest operation system ! keep this in mind that the operation system of my computer as the host computer, is windows 7 (64 bit)! does anyone have an idea how to solve this problem ?