OK, after building a new system from scratch and producing the same behavior, I believe I've confirmed this to be a configuration problem in Windows 2003. Here are the steps to reproduce: 1. Start with clean Windows 2003 (I did a fresh install). 2. Install EITHER the Windows Component Update files or use the VS.NET 2005 March 2004 preview installer to do a full VS.NET install with WCU files. 3. Apply HKLM\Software\Microsoft\ASP.NET\2.0.40301.9 corrupted registry key fix as per ReadMe file (Result: can use IIS MMC Properties dialog again) 4. Launch IIS MMC and create a web site and application 5. Try to access that site (Result: any page with .aspx suffix will result in "Page Not Found" error) 6. Try c:\windows\microsoft.net\framework\v2.0.40301\regiis_aspnet.exe -i and repeat steps 4 and 5 (Result: any page with .aspx suffix will result in "Page Not Found" error) [NOTE: this step will cause the corrupted registry key in (3) to reappear; you will need to fix it again] COMPARATIVE testing: - tried this on three separate Windows 20003 Enterprise Edition servers (two physical machines, one OS rebuilt 2x); same results - tried same thing on a Windows XP Pro SP1a machine and had no problem with pulling up the website in step (5) above Frederik or others: I have been unable to locate the appropriate MSDN 'beta' newsgroups for the VS.NET 2005 March 2004 Preview, so I can't be sure this will get posted to the right place. If someone knows how to get the word to the right people on the ASP.NET team, I'd be grateful (and, please, let me know how to do that, if appropriate :-). Regards, /s/ James