Everyone's excited about the free Windows 7 Beta download Microsoft's handing out tomorrow, but there's a catch: it's only available to the first 2.5 million downloaders. Here's how to make sure you're one of them. According to Wired—which pulled the details from this official Windows blog post—you'll need to grab the download from a link on the Windows 7 page as soon as possible once Microsoft begins the release. To get a product key to use with the download, you'll have to go through a registration process with Microsoft. Be sure to check out the full Wired post for a look at a few more possible gotchas. Then again, if you aren't lucky enough to make the cut tomorrow, there's always BitTorrent.