Axel and I have a new release of ROOT Builder up on source forge - v1.31 (see sourceforge.net/projects/root-builder/). This is a Windows install that makes it a bit simpler to build and run/debug ROOT on windows. It is a small GUI that will parse through the windows files and generate a Visual Studio 2003, 2005, or 2008 project. You can then hit build to build it (or debug it).
This latest build includes changes to build tools to build v5.22 and later versions of root. I’ve tested it on Vista, and Windows 7, and Axel has tested it on XP.
Please let me know if you have trouble!