The latest release of alfresco 2.1 does not have the java folder.
Have you set your BASEDIR properly.It should point to <alfresco root folder>/tomcat .I would suggest do that first and then try again.
Your Java_home and jre_home should point to a valid location where your jdk and jre folders are present.
Then try running setclasspath.bat from command line inside <alfresco-folder>/tomcat/bin. You can track your errors if any there.
try restarting your machine before or after making the changes.
let me know if it worked fyn.
best of luck