if u have created a restore point.than restore ur computer on that date..pls always make a resoting point.. if this does not work than try the best suited condition of safe mode..by pressing f5 at the time of booting..if then also it does not work then the solution is repair ur window,,if then also then remove un used software and if after all this it does not work... then my frnd format it,make a data backup of only important files and pls try avoid making back of any .exe software as it may be affected by any virus..and when u will again install it it will create the same prob again... hope ur problem will be removed....