My laptop not working

Hello,
I am Bharat from USA. I have dell inspiron 1420. I have bought it in 2008 March. At present its not working. I have sent it to dell for servicing. I dont know what repair they have done. It is as before and I got letter from them to replace the battery to new one. The problem is when I turn on its not showing anything on the screen some time dell logo is appearing and then get restart. I want to know that the system performance effects if the battery is not working? So It will be sure that my system works if I replace the battery?