If you've tried the Windows 8 Consumer Preview already then it's likely you dislike Metro UI very much. Want to get back the old Start Menu? Officially, it's gone. The new Metro Start Screen has replaced the Start Menu in Windows.
Thankfully, there's 3rd party options out there you can make use of. One such option is Classic Shell. The classic Windows Start Menu is just an install away.
Classic Shell even disables the Start Screen hot corner so you can't accidentally open up the Metro Start Screen instead.
Don't like the default looks? There's quite a few skins to choose from, and each comes with a set of tweaks you can play around with to get the Start Menu just the way you want it to be. Select All Settings right at the bottom and you can get even more settings to play to your heart's content.
You can download Classic Shell here.