The file was released by a group which calls themselves BILLGATES, it's 2.49GB and I've noticed people have released activation cracks and serial key generators a few hours ago.
I'm not sure if this version works but I assume it does. Some people in the comment section at Pirate Bay have problems installing or running the file but others say it works. Some people say you can run it without a serial number and that Windows Vista gives you 30 days to enter the code.
I guess Microsoft will be pissed. The final version of the operating system where they spend billions of dollars on is already available on the Internet almost three months before it will be available in retail stores.