Using phpMyAdmin:

1. Open up phpMyAdmin
2. Click on the Storage Engines link on the main screen
3. If InnoDB is enabled, it will show up in blue color

You can also check if InnoDB is enabled from shell. Connect to MySQL and run the following query:

mysql> SHOW ENGINES;
+------------+----------+----------------------------------------------------------------+
| Engine | Support | Comment |
+------------+----------+----------------------------------------------------------------+
| MyISAM | DEFAULT | Default engine as of MySQL 3.23 with great performance |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables |
| InnoDB | YES | Supports transactions, row-level locking, and foreign keys |
| BerkeleyDB | NO | Supports transactions and page-level locking |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) |
| EXAMPLE | YES | Example storage engine |
| ARCHIVE | YES | Archive storage engine |
| CSV | YES | CSV storage engine |
| ndbcluster | DISABLED | Clustered, fault-tolerant, memory-based tables |
| FEDERATED | YES | Federated MySQL storage engine |
| MRG_MYISAM | YES | Collection of identical MyISAM tables |
| ISAM | NO | Obsolete storage engine |
+------------+----------+----------------------------------------------------------------+
12 rows in set (0.00 sec)

If InnoDB is enabled, it will have a YES next to it.