If you are looking to find where that beta that Steve Ballmer promised at the keynote for Windows 7, the successor to Windows Vista; you might as well wait until CES is over because Microsoft is no longer offering the download link because of the demand.
Don’t worry, they will put it back up, eventually, as they are installing brand new servers to cope with the demand of the beta of Windows 7.
“Due to very heavy traffic we’re seeing as a result of interest in the Windows 7 Beta, we are adding some additional infrastructure support to the Microsoft.com properties before we post the public beta. We want to ensure customers have the best possible experience when downloading the beta, and I’ll be posting here again soon once the beta goes live. Stay tuned! We are excited that you are excited!” a person from Microsoft wrote on a blog post.
While I might suggest you should just go over to BitTorrent and get it from there; don’t! Just wait until the link is back up.