Firstly, thats far from a decent gaming system... Its a top end ripping fast one really.. It will handle any game you throw at it unless you have a ginormous 30 inch monitor
I suggest you save your money and download the Windows 7 beta, and install that. If you happen to have an extra copy of XP or Vista lying around you could try dual booting with Win 7. When Win 7 comes out next year simply buy the retail and replace your beta.
As for the beta being too buggy for your main OS, its not. Its actually very stable from my and many other people's experience and has some decent support going on for it. Plus its free for now.