How to enable InnoDB, which was previously disabled with skip-innodb option.

Case 1: Disabled the innodb with skip-innodb option and show engines givens as below.

  Engine     | Support ...
| InnoDB     | NO   ......

Case 2: As I want to enable the innodb, I commanded the #skip-innodb option and restarted. But now the show engines even not showing the InnoDB engine in the list. ?

Mysql Version : 5.1.57-community-log OS : CentOS release 5.7 (Final)

Log:

120622 13:06:36  InnoDB: Initializing buffer pool, size = 8.0M
120622 13:06:36  InnoDB: Completed initialization of buffer pool
InnoDB: No valid checkpoint found.
InnoDB: If this error appears when you are creating an InnoDB database,
InnoDB: the problem may be that during an earlier attempt you managed
InnoDB: to create the InnoDB data files, but log file creation failed.
InnoDB: If that is the case, please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.1/en/error-creating-innodb.html
120622 13:06:36 [ERROR] Plugin 'InnoDB' init function returned error.
120622 13:06:36 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
120622 13:06:36 [Note] Event Scheduler: Loaded 0 events
120622 13:06:36 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.1.57-community-log'  socket: '/data/mysqlsnd/mysql.sock1'  port: 3307  MySQL Community Server (GPL)