What virtual machine manager are you using to create and run your VMs? Hyper-V? VirtualBox? It makes a difference.
However, usually all you have to do to "clone" your VM is to copy the virtual hard drive file to the other PC and then install the same virtual manager there (such as Virtual Box). Then, from the VM manager software, create a new VM for the same OS as the other, then just attach the virtual drive to that VM and you should be all set. I've done it numerous times with Microsoft's Hyper-V and that's all there is to it. The virtual hard drive file contains the virtual operating system, you just need to tell the VM software what's on the virtual drive (Windows XP, Windows 7, etc.) then start it up.