Here are some tips that I hope will help someone avoid the frustration that I went through in installing DNN4.03 on a win 2003 server with ASP.Net2.0x

Follow the directions in the install package.
AND in addition to giving the ASPNET and NETWORK SERVICES users 'modify' permissions on the <dotnetnuke> directory, give the <root> of whatever the default directory that's hosting the DotNetNuke virtual directory the same permissions (e.g. <wwwroot>.
Make sure that IIS manager is allowing ASP.net2.0x (under "web service extension" (by default a clean install is locked down).
Make sure that the virtual directory is showing as using asp.net2.0x (even after installing 2.0x, the directory was showing 1.xx)
Make sure that SQLExpress is using mixed authentication (default is windows only)
I could not get the SQLExpress <connection> or <app settings> strings in web.config to work.  Instead I used the Server 2005 strings.
It now works. Yay.

SORRY. it doesn't work. there must be some asp.net2.x stuff that's going on that voids some of the javascript.  inventua.com's solution doesn't work, so if you're still having problems, don't fork over the bucks. I think that you are better off going with postnuke... it DOES work as advertised with installation instructions as advertised.  Too bad. DNN3.x on a 2000- server worked nicely.



Sorry, I wrote the above out of frustration



the above DOES work. I experienced problems that miraculously corrected themselves the next morning. Probably I was filtering events through the filter.