Newbie question about loading servlets on tomcat

I have what is probably a very basic question about loading simple servlets on to tomcat to test its installation. I have followed instructions from numerous tutorials to the letter but still I can't get it to work.
I have installed tomcat on win2k in c:\tomcat. I set up the jdk, environment vars (JAVA_HOME, CATALINA_HOME, TOMCAT_HOME) which all point at the correct dirs. I can compile a servlet without errors. I can also place a test jsp and html file into the root directory and they both work fine.
However, now I am trying a test servlet and no matter what I do it gives me a 404. I have a servlet class file called "HelloServlet.class" which I placed into the %install_dir%\webapps\ROOT\WEB-INF\classes directory. I try to reference it using this url:
http://localhost/servlet/HelloServlet
Tomcat is configured to use port 80 and has been restarted after adding the servlet class file. Does anyone have a clue why this is not working for me?
Many thanks
Marc

You have to add in the web.xml file that it is in the WEB-INF dir, the information about your servlet. An example:
<web-app>
<servlet>
<servlet-name>HelloServlet</servlet-name>
<servlet-class>HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/HelloServlet</url-pattern>
</servlet-mapping>
</web-app>

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