Came across a box today which was returning a 405 – Method Not Allowed error when I tried running ASPX pages. Checking IIS, I found that somehow, there was no ASPX extension registered in the Application Mapping section of IIS. My first reaction was to reinstall the .Net Framework 1.1, but this didn’t cure the problem.
Once again, Google came to the rescue, thanks to which I found a posting which contained the solution to my problem:
If you run “c:\winnt\microsoft.net\framework\{version of CLR}\aspnet_regiis.exe -I”, this will re-register ASP.NET and *should* fix up IIS settings for you
Worth keeping in mind in case I run into it again !!