Blank screen upon Booting

I am trying to repair a problem in DELL Inspiron 510m. When I switch on, there is a series of beeps and the Win XP starts and then there is a blank blue screen. No Start button, No Task bar. Mouse cursor is present and responds. But Right click produces no result. By pressing control-alt-del one can access any application and start that. But this is obviously a cumbursome way to work. Shall be grateful for some hints and help