There are other ways...
One other thing you might think about. There is software such as VirtualBox which you can run on top of your OS (Linux or Win 7 or 8, though I would stay with Win 7 unless I had another reason to run 8) because it lets you run other operating systems concurrently on the same box, on a different network. There are other choices but this is without further out of pocket cost, and it works pretty well. I have Win 7 and 8 and XP and another Linux on this box, all able to spin up simultaneously, so it is kind of handy. There are other options but this one works, it's relatively easy to use, and there are a lot of users and an IRC channel if you need to figure something out.
https://www.virtualbox.org/
https://www.virtualbox.org/wiki/Downloads
Find an empty machine, install Linux or Win 7, do your updates, then install VirtualBox. You then create one or more "virtual machines", and into one of those a new install of XP. While still in it's default mode you install all the updates, and Security Essentials (which they are going to continue to update for a year or so, if Security Essentials is installed by 4/8/14). Then your stat package, and any updates it needs.
Then you create a new "virtual switch" inside VirtualBox (sounds harder than it is, trivial after the first time or two) and connect the new virtual OS to that. Then it can run on that box, communicate with that box, but not communicate with the outside.
So you can run your stat package, on XP, on a more secure machine. XP will still be a problem if you connect it to the network, but if keep it on a private address (192.n.n.n or something that is not routed onto the Internet), and don't browse to anyplace except MSfor the updates, you will be reasonably secure.
Periodically you can restart, swap your "virtual switches" and download any new updates, then switch it back.
The other nice thing is that it creates its own "vdi" file, an image which you can backup after you get it set up how you want. Anytime you need a fresh install, just copy that vdi file back onto the machine, and tell VirtualBox to spin it up. Poof, just like day 1 again, then you just install any new updates there are for Security Essentials.
Anyway, it's another option for you.
