How to reduce Original Cost of Asset without affecting Depreciation Reserve

Hi

We have receivied subsidy from Govt for one of our location, which are Asset Capital in FY10. Now we want to reduce Original Cost of Asset without affecting Depreciation Reserve acculated till 31st Mar'12. 

Following is scinario for your reference

Date of Capitalisation : 1st April, 2010

Original Cost of Asset       : 1,00,000/-

Depreciation Reserve        : 10,000/-

Net Book Value                  : 90,000/-

Depreciation Rate              : 10%

Above details of Asset as on 31st Mar'12.

Now we want to reduce Cost of Asset for Rs. 25,000/- * without affecting Depreciation Reserve.  I am giving below the requirements for FY 2012-13 ( 1st Apr'12 to 31st Mar'13). 

Original Cost of Asset       : 75,000/-  ( 1,00,000 - 25,000* )