hadoop WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
There are no native hadoop libraries for Windows (see Native Libraries Guide so the warning is expected and it's just a warning, not an error. The same applies for Mac OS X environments, no native libraries provided either.
If you want to suppress the WARN just edit the $HADOOP_CONF_DIR/log4j.properties (usually something like etc/hadoop/log4j.properties) and add the following:
log4j.logger.org.apache.hadoop.util.NativeCodeLoader=ERROR Only errors (and not warnings) will be logged from now on.