Use:
Sys.setenv(JAVA_HOME='...path to JRE...')
e.g.
Sys.setenv(JAVA_HOME='C:\\Program Files\\Java\\jdk1.7.0_51\\jre')
Your environment variable is wrong.
Use:
Sys.setenv(JAVA_HOME='...path to JRE...')
e.g.
Sys.setenv(JAVA_HOME='C:\\Program Files\\Java\\jdk1.7.0_51\\jre')
Your environment variable is wrong.