Error after accesing asp files

Hi ,i have installed iis 5.1 in my windows xp pro , and if i write http://localhost ,i can read html files ,but not asp files i recive a server aplication error

What's wrong?

Thanks for your help

What error are you getting. Any specific message.

What is the code that you have written in the asp page?

You will have to provide more info.

ASP or ASP.NET?

Be very sure. If it's ASP.NET, you'll need to create a virtual directory, have the framework installed, blah blah balh

It's a asp.net ,firts i had a message like that:
Error 500 inside server or something like that, after thought internet i read that i had to put in Explorer-Tools-Options-Advanced Tools-And quit something like "Show descriptive messages about http error". After quit it ,when i put a asp files in http://localhost/index.asp i recive this message:

"Server Application Error

The server has encountered an error while loading an application during the processing of your request. Please refer to the event log for more detail information. Please contact the server administrator for assistance"

Framework it's installed ,i put in Windows Update and i have downloaded all.

I have a postinfo.html ,with a message about information about the web ,i renamed this file to a postinfo.asp ,but also the same , so it's very strange that i can read html files but not asp files.

Thanks

Did you run aspnet_regiis -i?
Did you create a virtual directory for the web application?
Did you make it as a web application or did you simply create the aspx out of notepad?

1) i didn't run aspnet_regiis -i ,how i have to do it?
2) I have created a virtual directory ,to a refence a "My documents" ,another to reference to c:\Inetpub\wwwroot with "my_documents" and "hello" names but also the same error
3) I did'nt created a web page, just a notepad file

Thanks

1. Go to your framework folder (navigate to it in Command Prompt), and run aspnet_regiis -i
3. So you're not using Visual Studio or any other IDE?

I do it ,but also the same: the file results its' these one:

-----
File Attached

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I have instaled Visual Studio .Net 2002 and 2003
Frameworks: 1.0.3705,1.1.4322,2.0.50727