Today I installed IIS 5.0 on my new Win 2000 machine at office. Surprisingly, no ASP page would work on my system. ASPX, HTML pages worked beautifully. I was confused. I searched in the Net and came across the article by Microsoft on how to troubleshoot this issue.
In fact, it is a problem with the IWAM_##Computer Name## account. This user needs to be added to the Local Administrators group. Now my problem is solved.