Ed Bott has written a Metro removal guide for Windows 8.1 Preview.
http://www.zdnet.com/the-metro-haters-guide-to-the-windows-8-1-preview-7000018398/
Personally I'm going to wait for StartIsBack, Start8, Classicshell and others to release their Windows 8.1 compliant versions, presumably when Windows 8.1 releases officially, but the linked article should ease most of the pain if you're deadset on running the 8.1 preview.
http://www.zdnet.com/the-metro-haters-guide-to-the-windows-8-1-preview-7000018398/
Personally I'm going to wait for StartIsBack, Start8, Classicshell and others to release their Windows 8.1 compliant versions, presumably when Windows 8.1 releases officially, but the linked article should ease most of the pain if you're deadset on running the 8.1 preview.