Hi ankit,

You can use use msg.exe 
(a new command line tool that more or less replaces the infamous "net send"). 
C: Windows system32>msg /?
Send a message to a user. 

MSG {username | sessionname | sessionid | @filename | *}
 [/SERVER:servername] [/TIME:seconds] [/V] [/W] [message] 

 username Identifies the specified username.
 sessionname The name of the session.
 sessionid The ID of the session.
@filename Identifies a file containing a list of usernames,sessionnames, 
and sessionids to send the message to.
 * Send message to all sessions on specified server.
 /SERVER:servername server to contact (default is current).
 /TIME:seconds Time delay to wait for receiver to acknowledge msg.
 /V Display information about actions being performed.
 /W Wait for response from user, useful with /V.
 message Message to send. If none specified, prompts for it or reads from stdin. 

Running a command like this one:

C: msg /server:Ankit philips "Please contact immediately!"

Will result in a message being sent to the Ankit computer, to philips session.

the MSG.EXE command does NOT require the Messenger service to be running on the target computer.