Thanks. Found it. Doesn't matter though because after it scanned my system it said I did not meet the requirements to play it. Said it required a minimum 2.9ghz processor and mine is only 2.6. And my video card needed to be at least a 6800gt and mine is only a 6600. So, I passed.
You should still be able to run it fine, and your 6600 will do the HDR lighting effects. It's short but IMHO worth it to check out some of the new effects and the commentary. You should try it if that interests you.
However, for those who don't have an HDR-capable card, then it is mostly pointless.