By Default, on Windows 2003 server IIS 6.0 ASP.Net is disabled. One need to enable it to run the ASP.net on the server. To enable it one needs to perform below mentioned steps:
1) Open Control Panel from windows 2003 server.
2) Click on Add Remove programs.
3) Click on Add/Remove Windows Components.
4) Click on Application server and click on details.
5) In that window, select the check box against the ASP.Net and click on OK.
6) Now open IIS 6.0.
7) Click on your computer name -> Web Server Extensions.
8) Make sure "ASP.NET" has a check mark next to it, and that means that it is enabled.
Now, ASP.Net pages should be working fine for the server.