Well, than it will pay off for you either way : ) That is where the retail W7 is good : ))
Try it to swap it and than u will see. Drivers are the important thing here.
But if u want the best performance, just reinstall.
Make sure u get the drivers from the manufactures website, as there are the newest ones.
Get them before the swap.
Get them herehttp://www.asrock.com/mb/download.asp?Model=Z68%20Extreme7%20Gen3&o=Win764