Newbie Tomcat 4.0 install gives 500 "No Context configured" error @ HTTP localhost

Installed Tomcat 4.0 (my professor recommended this older version) on my Win 2000 box. j2sdk1.4.0_01, j2sdkee1.2.1. Before installing Tomcat, I changed my Oracle XDB port to use 8083 instead of 8080. IIS is also installed, uses port 80. I have Norton Internet Security (yes, it makes my life difficult) but it's disabled right now.

It feels like maybe an Apache thing, but then again Tomcat is working enough to tell me that the examples directory isn't available, so I am truly lost. Don't know which errors are most important so I'll throw them all out there. I Googled on all of them, but could find no solution, even though I know this question and variants has been asked many times. Please go easy on this Java newbie...

My Catalina DOS window that comes up when I invoke startup shows:
Starting service Tomcat-Standalone
Apache Tomcat/4.0.1
Starting service Tomcat-Apache
Apache Tomcat/4.0.1

... I have a feeling it should say more than that, but as a newbie I have no idea.

When I go to http://localhost:8080/ I get an error "HTTP Status 500 - No Context configured to process this request"

When I go to http://localhost:8080/examples/ I get an error "The requested resource (/examples) is not available."

My apache log in the tomcats logs folder says:
2005-04-28 23:09:29 [org.apache.catalina.connector.warp.WarpConnector] Error accepting requests
java.net.SocketException: socket closed
      at java.net.PlainSocketImpl.socketAccept(Native Method)
      at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:343)
      at java.net.ServerSocket.implAccept(ServerSocket.java:438)
      at java.net.ServerSocket.accept(ServerSocket.java:409)
      at org.apache.catalina.connector.warp.WarpConnector.run(WarpConnector.java:580)
      at java.lang.Thread.run(Thread.java:536)

Catalina log says:
2005-04-28 23:29:53 HttpProcessor[8080][4] process.invoke
java.lang.NullPointerException
      at org.apache.catalina.valves.ErrorDispatcherValve.status(ErrorDispatcherValve.java:280)
      at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:180)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:462)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:163)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1011)
      at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1106)
      at java.lang.Thread.run(Thread.java:536)

Localhost log is saying something different now than half an hour ago---I think all I did in between was stop IIS even though it's on another port:
2005-04-28 23:09:39 StandardContext[/manager]: Error initializing resources: Document base C:\tomcat4\webapps\manager does not exist or is not a readable directory
2005-04-28 23:09:39 StandardContext[/manager]: Context startup failed due to previous errors
2005-04-28 23:09:39 StandardContext[/manager]: Exception during cleanup after start failed
LifecycleException:  Container StandardContext[/manager] has not been started
      at org.apache.catalina.core.ContainerBase.stop(ContainerBase.java:1147)
      at org.apache.catalina.core.StandardContext.stop(StandardContext.java:3440)
      at org.apache.catalina.core.StandardContext.start(StandardContext.java:3397)
      at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1123)
      at org.apache.catalina.core.StandardHost.start(StandardHost.java:612)
      at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1123)
      at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:307)
      at org.apache.catalina.core.StandardService.start(StandardService.java:388)
      at org.apache.catalina.core.StandardServer.start(StandardServer.java:505)
      at org.apache.catalina.startup.Catalina.start(Catalina.java:776)
      at org.apache.catalina.startup.Catalina.execute(Catalina.java:681)
      at org.apache.catalina.startup.Catalina.process(Catalina.java:179)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:324)
      at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:243)
2005-04-28 23:33:01 StandardHost[localhost]: MAPPING configuration error for request URI