Reminder for outstanding processed at cpc for ay 2009-10

As a novice I have filed income tax online for the Assessment Year 2009-2010 in January 2011. And as consequence I have done some serious mistake on income figures. Now on 29th Mar, 2012 I have received a "Reminder for Outstanding Payment processed at CPC", demanding a huge tax to paid (Rs. 36450/-). Mentioning that, "Verification of records shows that the following Demand/s as raised in the demand notice mentioned above is/are still
outstanding and are payable by you.". I am at my wit's end, what to do at present situation.

Please help.