The cool part about MobaLiveCD is that it's not only portable, it's designed to be portable. That is, it has an option to install a "Right-click association," meaning that you can right click any ISO files and it will show an option for MobaLiveCD. But the real nice thing is that you can add and remove that association with a click of the mouse. Click "Install" and it's there, click "Uninstall" and it's gone.
So once you pick your ISO file, you have an option of creating a virtual hard disk for it. Your live CD pops up in a window, just as it would if it were on a separate computer. That's about it! Moba makes it really easy to run your live ISOs. The window is NOT resizable, but you can go fullscreen, which is very nice to see how the live CD will look on an actual monitor, not in a window.
The point of MobaLiveCD is not actually to be a virtual machine that is used for an extended period of time (ie, installing Linux inside of Windows and using it often), but instead, it is meant to "test live CDs". Because it's not meant to be as complicated as other virtual machines, there are some limitations. First off, it can only handle ISO files. Secondly, it has the bare bones in terms of customization (RAM amount, USB devices, etc). Lastly, it doesn't appear to be able to boot from a virtual hard disk. You might be wondering "Then why do you have an option to create one?" I'm wondering that as well....I'm guessing it's because maybe you want to attempt to install (like from an Ubuntu Live CD) and you want to give it a test try, then you can. But otherwise, it looks like it's more of a "session-by-session" deal.
So for being a tool to "test Live CDs", it performs EXTREMELY well. Compared to other virtual machine programs, it may seem a little limited, but I prefer the term "lite". Great for if you want to just try out an ISO for a new Linux distribution, or just like to keep a VM program on hand at all times.