Error while trying to run project

[Luis Esteban Valencia]

I was working on a project ASP.Net
and it was working properly before I reformatted the OS

I setup a new OS Win XP Pro and V. Studio Enterprise Architech 2003

I wanted to add some more things and compile it

Now i got the following error when i try to run the project

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Error while trying to run project: Unable to start debugging on the web
server. The project is not configured to be debugged.

Click Help for more informarion.

-- OK-- -- HELP --
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from http://localhost/webapp1
it runs, working fine

I can create new web application on VStudio (It runs)