Sony VAIO Laptop Eh25en — system hang

Address:

Kerala

sir,
I purchased a sony vaio laptop from comsol pvt ltd ho trivandrum on 25/01/2012 product key-YVJ9F-MHGM9-79DDY-GKYQJ-F6DDPJ. From the first week itself it was not working properly. I consulted a sony authorized service center at plamood jn trivandrum on 04/02/2012. they done something and at that time it was working. but after a few hours later the problem again started. Then on 18/02/2012 i again consulted the same service center..Then also they done something and at that time also it was working. But now the thing is that the problem is still there. Then i called on your toll free number. Mr.Chandan was on line and he said that a formatting is needed. I'm not interested to go for servicing regularly. What is the next step i have to follow?