Are you really asking about virtual machines? I echo what Joe C said above, I have never heard of a virtual motherboard.
Virtual machines are legit and are very useful but in order to run a VM, you need to have a working physical machine so if you are having problems with your computer then you probably won't be able to run a VM.
There are 3 decent, free, VM tools MS Virtual PC, Oracle VirtualBox and VMWarePlayer. In order to create a virtual machine with any of these tools, you need to have the OS disk and a product key to install, just as you would with a physical machine.
If you are running Win 7 Pro or Ultimate then you are eligible to download XP Mode from MS which is a Virtual PC VM that includes a fully licensed copy of Win XP.