followed the simple steps on this page: https://wiki.jenkins-ci.org/display/JENKINS/Upgrading+from+Hudson+to+Jenkins
"Basics

Jenkins is basically a drop-in replacement to Hudson. It understands the same set of environment variables, same system properties, and the same information in the home directory. So if you rename jenkins.war as hudson.war, and simply overwrite your hudson.war, the upgrade is complete."

started the server with the following command:
java -DHUDSON_HOME="D:\BUILD-ACCOUNT\Hudson\Home" -jar "D:\BUILD-ACCOUNT\Hudson\hudson.war" --httpPort=9292 --ajp13Port=9209

And got the following output:

Running from: D:\BUILD-ACCOUNT\Hudson\hudson.war
webroot: System.getProperty("HUDSON_HOME")
[Winstone 2011/06/02 17:37:15] - Beginning extraction from war file
hudson home directory: D:\BUILD-ACCOUNT\Hudson\Home found at: System.getProperty("HUDSON_HOME")
[Winstone 2011/06/02 17:37:16] - HTTP Listener started: port=9292
Using one-time self-signed certificate
[Winstone 2011/06/02 17:37:16] - AJP13 Listener started: port=9209
Jun 2, 2011 5:37:16 PM hudson.model.Hudson$5 onAttained
INFO: Started initialization
[Winstone 2011/06/02 17:37:16] - Winstone Servlet Engine v0.9.10 running: controlPort=disabled
Jun 2, 2011 5:37:16 PM hudson.model.Hudson$5 onAttained
INFO: Listed all plugins
Jun 2, 2011 5:37:16 PM hudson.plugins.greenballs.PluginImpl start
INFO: Green Balls!
Jun 2, 2011 5:37:16 PM hudson.model.Hudson$5 onAttained
INFO: Prepared all plugins
Jun 2, 2011 5:37:16 PM hudson.model.Hudson$5 onAttained
INFO: Started all plugins
Jun 2, 2011 5:37:16 PM hudson.model.Hudson$5 onAttained
INFO: Augmented all extensions
Jun 2, 2011 5:37:16 PM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field cleanWorkspaceRequired
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.model.FreeStyle
Project.cleanWorkspaceRequired
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaRefl
ectionProvider.java:152)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:229)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:180)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.j
ava:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStra
tegy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:926)
at hudson.util.XStream2.unmarshal(XStream2.java:80)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:912)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:856)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:113)
at hudson.model.Hudson$13.run(Hudson.java:2354)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$4.runTask(Hudson.java:735)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jun 2, 2011 5:37:16 PM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field cleanWorkspaceRequired
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.model.FreeStyle
Project.cleanWorkspaceRequired
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaRefl
ectionProvider.java:152)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:229)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:180)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.j
ava:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStra
tegy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:926)
at hudson.util.XStream2.unmarshal(XStream2.java:80)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:912)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:856)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:113)
at hudson.model.Hudson$13.run(Hudson.java:2354)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$4.runTask(Hudson.java:735)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jun 2, 2011 5:37:16 PM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field cleanWorkspaceRequired
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.model.FreeStyle
Project.cleanWorkspaceRequired
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaRefl
ectionProvider.java:152)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:229)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:180)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.j
ava:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStra
tegy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:926)
at hudson.util.XStream2.unmarshal(XStream2.java:80)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:912)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:856)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:113)
at hudson.model.Hudson$13.run(Hudson.java:2354)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$4.runTask(Hudson.java:735)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jun 2, 2011 5:37:16 PM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field cleanWorkspaceRequired
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.model.FreeStyle
Project.cleanWorkspaceRequired
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaRefl
ectionProvider.java:152)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:229)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:180)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.j
ava:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStra
tegy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:926)
at hudson.util.XStream2.unmarshal(XStream2.java:80)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:912)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:856)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:113)
at hudson.model.Hudson$13.run(Hudson.java:2354)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$4.runTask(Hudson.java:735)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jun 2, 2011 5:37:17 PM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field cleanWorkspaceRequired
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.model.FreeStyle
Project.cleanWorkspaceRequired
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaRefl
ectionProvider.java:152)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:356)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:229)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:180)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.j
ava:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStra
tegy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:926)
at hudson.util.XStream2.unmarshal(XStream2.java:80)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:912)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:856)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:113)
at hudson.model.Hudson$13.run(Hudson.java:2354)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$4.runTask(Hudson.java:735)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jun 2, 2011 5:37:18 PM hudson.model.Hudson$5 onAttained
INFO: Loaded all jobs
Jun 2, 2011 5:37:18 PM hudson.model.Hudson$5 onAttained
INFO: Completed initialization
Jun 2, 2011 5:37:18 PM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 58516