I have to develop and support three versions of .Net projects on one Windows 7 machine running IIS7. After installing VS2003, VS2008 and VS2010 on the machine, it was not without some struggling to get the legacy .Net 1.1 project to run seamlessly in IIS7, so it is worthwhile to write down a few key steps here:

1. Created a .Net 1.1 website, called Net1_1 in IIS7 and selected Application pool ASP.Net 1.1 from the available Application pool drop-down. The ASP.Net 1.1 application pool was created automatically when Framework 1.1 was installed. If this application pool is not present, that is an indication that .Net 1.1 framework has not been installed or was not installed properly.
2. Made sure that the ASP.Net 1.1 app pool “Managed Pipeline Mode” is “Classic”, which is default, instead of “Integrated”.
3. At this point, I tried to browse to the .Net 1.1 app directly from IIS7, I got all sort of errors. They were caused by that ISAPI filter for .Net 1.1 was not  present by default in IIS7. To fix that, I selected the Net1_1 site -> Features View and double-clicked on “ISAPI Filters” icon; clicked on Add, gave it a name “Asp.Net 1.1″ and set “Executable” to be “C:\Windows\Microsoft.NET\Framework\v1.1.4322\aspnet_filter.dll”.
4. Lifted the ISAPI and CGI restriction on the filter by going in to ISAPI and CGI Restrictions pane (accessed from Machine level Feature View) and changed Restriction from “Not Allowed” to “Allowed”.
5. Almost done; I still got “Access denied” error after all these, why? Googled for “running .net 1.1 on IIS7″ and found a useful post at http://blogs.iis.net/rakkimk/archive/2008/03/20/iis7-running-asp-net-1-1-applications.aspx, which pointed me to download and install .Net framework 1.1 service pack 1. After that, I was able to bring the .Net 1.1 site back to live in IIS7!
6. Another error, “Error while trying to run project: Unable to start debugging on the web server. Access is denied.”, arose when I tried to debug the .Net 1.1 project from VS2003. What’s going on? Well, it’s the notorious Windows 7 “Run as Administrator” thing! I had to run VS 2003 as administrator, open the project from VS2003, and then the error went away. What an inconvenience!