tecra laptop: hd,screen and mouse locks up?

sometimes it will boot and then hd light goes out mouse wont work .sometimes it wont boot at all.when yoiu turn it on hd light turns on then goes off. it had win 2000 on it,i tried to install dvd drive it shut down so i put back the cdrom. i reinstalled win2000 and that did not help so i installed xp3 and the problem is still there