Table 'mysql.user' doesn't exist:ERROR

I am creating a db in mysql for a java program.My program works well in my friends system.But I have some problem with my mysql.

The query is below:

mysql> create database sampledb;

Query OK, 1 row affected (0.00 sec)

mysql> use sampledb;

Database changed

mysql> create user zebronics identified by 'zebra123';

ERROR 1146 (42S02): Table 'mysql.user' doesn't exist

I cant create any user for my db.Please help??