When I attempted to open a solution or a project in VS.net 2003, I got the error "Visual Studio.net has detected that the web server is running asp.net version 1.0..."  I tried all the suggested fixes.  I re-registered aspnet via the regiis utility.  I registered my aspnet_isapi dll via regsvr32.  I tried changing my web service extensions settings.  I even deployed a physical Get_aspx_ver.aspx file.  None of these fixes did the trick

If I cancelled out of converting the solution after receiving this message, I would then get an error that the projects had been moved or removed until i restarted iis.  Nice.

Eventually, I gave up and decided that it wasn't important enough for this particular project to be 1.1 ready.  So I deleted the solution and opened the desired project by itself.  No error...  Then I added the other projects back in.  No ERROR?  sweet.  I guess

So, If you get this error when trying to open 1.0 projects in a win 2003 server with 1.1, try this silly work around.  It just might work.