any way for me to copy the media center 12 files from laptop and bring them into 13 on main machine? would that work?
Yeah. I think that'd be fine. You just need access to SOME installation of MC12 with G-Force installed in order to get the actual plugin files to install.
However, if you don't currently have G-Force installed on that machine at all (you never installed it before, or uninstalled it as well when you uninstalled MC12), it might be difficult to get G-Force to install if you don't have the Platinum version and it doesn't "detect" MC12 on the system. Even if you copy over the G-Force DLL files, you still need to have the actual application itself installed. It installs preference files and other DLLs and whatnot into its own folders during the install process. That needs to have been done no matter what player you're using.
With the Platinum edition this shouldn't be a problem because it works with multiple players. Just install it on the MC13 machine for Windows Media Player or something, and then copy the DLL files over from your machine where you have MC12 still installed. For the free version or Gold, it won't work that way because it is specific to your player. I've owned Platinum since before there even was a gold version, so I don't even remember how it works in detail.
If you don't own Platinum, and the current version of G-Force/WhiteCap isn't already installed on the system, the easiest thing will be to just re-install MC12 just for these purposes. You don't have to
use it, and it won't hurt anything to have it installed while you use MC13 (just don't try to use them both at the same time). This really could be handy to have for testing anyway, at least as a backup. Remember, MC13 is still a very early beta. You're treading in uncharted waters here! After you install MC12, then install G-Force/WhiteCap, and then proceed with these instructions...
EDIT: I moved the Instructions I wrote up over here, because that is a better spot for them to live long-term:
http://yabb.jriver.com/interact/index.php?topic=48384.msg331623#msg331623