Did you enable ASP.NET on IIS 6.0 ?
You have to specifically enable ASP.NET on IIS 6.0
You can enable ASP.NET by opening the IIS Manager and scrolling down the left-hand
side to "Web Service Extensions", click once on it and look on the right-hand panel.
Click once on the ASP.NET version you want to enable, and click the "Allow" button.