Very Very interesting indeed......
It can't be the 200Mhz difference, as that would not be noticeable. And I doubt it is the dual core either, as RR is not coded to take advantage of that. Hmmm
I installed Vista Ultimate on this PC a few months back to test, and see... It's a Legit copy, well sort of hahah! A friend got it for $20 at the college bookstore.
On my machine I found it to run slower. I ran some bench mark utility on XP before I formatted and installed Vista. Then ran the same test on Vista (After saying YES, that I really did want to download it, and YES I really do want to install it, and YES I really did want to run it ) , and over all it was about 30% slower.
After installing RR, I was getting strange incomplete skins, and bleeding of one thing into another. I never did quite resolve that, and I switched back to XP after a week. All this being said, I just find it interesting that RR is running so much faster for you.
Please lets not turn this into a Vista FanBoy thread, or Vista bashing thread either. There are thousands of other forums on the net for that! These were just my experiences with it when I tested it out.