使用phonegap / cordova时，'node'不会被识别为内部或外部命令，可操作程序或批处理文件

I am using phonegap/cordova. Everthing is installed propelry i.e cordova, phonegap, ant,sdk,jdk. But now it says "node is not recogzed as an internal or external command" Please help!I am using phonegap/cordova. Everthing is insta