Solr Configuration

I tried to installed Solr using:

java -jar start.jar

However I downloaded the source code and didn't compile it (Didn't pay attention). And the error was:

http://localhost:8983/solr/admin/

HTTP ERROR: 404
Problem accessing /solr/admin/. Reason:
NOT_FOUND 

Then I downloaded the compiled version of solr but when trying to run the example configuration I'm getting exception:

java.net.BindException: Address already in use 

Is there a way to revert solr configuration and start from scratch? Looks like the configuration got messed up. I don't see anything related to it in the manual.

Here is the error:

2011-07-10 22:41:27.631:WARN::failed SocketConnector@0.0.0.0:8983: java.net.BindException: Address already in use
2011-07-10 22:41:27.632:WARN::failed Server@c4e21db: java.net.BindException: Address already in use
2011-07-10 22:41:27.632:WARN::EXCEPTION 
java.net.BindException: Address already in use
    at java.net.PlainSocketImpl.socketBind(Native Method)
    at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:383)
    at java.net.ServerSocket.bind(ServerSocket.java:328)
    at java.net.ServerSocket.<init>(ServerSocket.java:194)
    at java.net.ServerSocket.<init>(ServerSocket.java:150)
    at org.mortbay.jetty.bio.SocketConnector.newServerSocket(SocketConnector.java:80)
    at org.mortbay.jetty.bio.SocketConnector.open(SocketConnector.java:73)
    at org.mortbay.jetty.AbstractConnector.doStart(AbstractConnector.java:283)
    at org.mortbay.jetty.bio.SocketConnector.doStart(SocketConnector.java:147)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.Server.doStart(Server.java:235)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.xml.XmlConfiguration.main(XmlConfiguration.java:985)
    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:597)
    at org.mortbay.start.Main.invokeMain(Main.java:194)
    at org.mortbay.start.Main.start(Main.java:534)
    at org.mortbay.start.Main.start(Main.java:441)
    at org.mortbay.start.Main.main(Main.java:119)
Jul 10, 2011 10:41:27 PM org.apache.solr.core.SolrCore registerSearcher
INFO: [] Registered new searcher Searcher@5b6b9e62 main