When I used the Tomcat 4.1.18, I copied the servlet.jar file from C:\jakarta-tomcat-LE-4.1.18\common\lib to the C:\j2sdk1.4.2\lib directory.
However, I do not find servlet.jar file in the Tomcat 5.0.27. I only find servlet-api.jar in the jakarta-tomcat-5.0.27\common\lib directory. Are servlet-api.jar (5.0.27 version) and servlet.jar (4.1.18 version) the same thing?
Effectively, yes. You need to use servlet.jar for Tomcat 4 and servlet-api.jar for Tomcat 5. I think 4 supports the Servlet 2.3 spec and 5 supports Servlet 2.4. I'm sure someone with greater knowledge than I will correct me if I'm wrong.
To use JSP 2.0 you probably need the JSP jar as well. But why are you copying them around? You should just leave them where they are and be sure they are included in the compile classpath (using Ant makes this simple).