Windows 7 RC with build number 7100 was released by Microsoft for download
on their official site
free. But yesterday was the last day for download and it ended today, no more downloads now but product key can be still grabbed from there. Microsoft updated their site reporting that no more downloads can be availed from there.
The Product key can be get only till 21st of October this year. So if anyone having Windows 7 RC then s/he can avail product key from here.