jQuery 1.3 can be downloaded from over here: Download Query 1.3
jQuery Intellisense with Visual Studio 2008
If you are new to jQuery intellisense in Visual Studio 2008, check one of my posts at dotnetcurry, Using jQuery with ASP.NET - A Beginner's Guide where I have covered it step by step.
Unfortunately the 1.2.6 VS 2008 intellisense documentation file does not work properly with jQuery 1.3. In order to use a intellisense documentation for jQuery 1.3, check James blog where he