Accounting of fixed assets - computer

as per your question, the replacement will enhance the performance of the asset, as per AS 10, if replacement would result in enhancement of performance than previously assessed performance then such expenditure would qualify for capitalization, but you should take decision after considering materiality aspect.that is  whether the amount of expenditure is such that should be capitalized or can be charged to profit and loss account.. 

while capitalizing both approaches shall be bourne in mind. .