from 6th March,2008 the first IE 8 public beta has released.

Windows Internet Explorer 8 Beta 1 for Windows Vista and Windows Server 2008

download it from: http://go.microsoft.com/fwlink/?LinkId=110325

Internet Explorer 8 Beta 1 for Windows Vista x64 Edition and Windows Server 2008 x64 Edition
http://go.microsoft.com/fwlink/?LinkId=110328

Quick DetailsFile Name: IE8-WindowsVista-x86-ENU.exe
Version: 8
Date Published: 3/6/2008
Language: English
Download Size: 11.0 MB
Estimated Download Time: 27 min 56K

IE8 for xp sp2: http://go.microsoft.com/fwlink/?LinkId=110324