how to get OS on virtual machine?

I just got virtualbox and now I need a OS to go on it. Is it possible to clone my existing hard drive and some how use it on the VM. What is the best way to go about this? I want to have 5 VMs

Any suggestions?

Download some .iso files either from linux websites like xubuntu, mint or download windows .iso files from thepiratebay and just create fresh new VMs. You load the .iso when you start up the first time. Takes maybe 20-40 minutes to install the OS.