Configuring Web site 'http://localhost/WebSite01' for ASP.NET 2.0 failed.

I have wanted to create a web service on a PS. On that PC there are: Microsoft .NET  Framework 3.5 SP1, Microsoft .NET  Framework 3.0 SP2, Microsoft .NET  Framework 2.0 SP2
When I try to create an ASP C# Web Service, I obtain this error:
Configuring Web site 'http://localhost/WebSite01' for ASP.NET 2.0 failed. You must manually configure this site for ASP.NET 2.0 in order to run correctly.
1. I want to develop my web service with net.frameworks 3.5 and Visual Studio Proffesional 2008.
2. I want to develop my web service with net.frameworks 3.5 and Web Developer Express 2008.
How can I debugg this ?
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