Sometimes, bad sector occurs in the hard disk of our computer. ‘Bad sector’ refers to damage of memory partly. That means, in which parts of the hard disk is affected by the bad sector problem, that parts can not preserve data. Which part of the memory remain unused for long time that parts may be affected by bad sector problem. So memory of the hard disk should not be kept unused for long time. If necessary, we can bring data from other drive and we can take data into another drive. Up and down of voltage may also create this bad sector problem .