One option that you might want to consider is getting Virtual PC 2004 from Microsoft. They have a free 40 day trial or there abouts. http://www.microsoft.com/windowsxp/virtualpc/ That will let you make a virtual installation of windows that you can try the beta software with and not risk your normal installation.
Virtual PC is pretty slick. If you want it past the 40 days or whatever, it's around 100 or 120 dollars.
VS.net 2003 and vs.Net 2005 seem to work together, but its .Net framework v2.0 which seems to have problems with IIS 6, because none of my ASP.NET 2 projects seem to work when 1.1 and 2.0 are installed on the same webserver