cannot Sql server agent Error 1053

Few months Back I have installed Sql Server 2008R2 in server,At the time of installation

1.Mixed Authen 2.Sql agent User name As NT Authority\NetworkService And same User name for all Other components Also.

At that time Every thing is soft But Now wen I start the Agent I am Getting this below error.

Windows could not start the SQL Server Agent (MSSQLSERVER) service on Local Computer. Error 1053: The service did not respond to the start or control request in a timely fashion.

http://support.microsoft.com/kb/322140

I followed this link Steps are not clear but tried few,Wen i run by using cmd as admin,i got below error.

The program can't start because sqlncli10.dll is missing from your computer. Try reinstalling the program to fix this problem.

Please any One help Me with easy steps..

Thanks in advance..

Prasad