i think you are a rough user of your computer,because you should understand that computer is also an electronic device like all other devices ,while keep on for a whole night it can even distroy your electronic circuits in side computer due to tramandus heat caused inside the cpu workingso now onwards please dont use computer roughlly like u did previous,now to solve this problem in your computer just remove your ram and reinsert again then switch onn computer then check the connectors of monitor and power cable of cpu,then try to switch onn your computer its working normally with a single beep during start up its ok other wise restart and change the bootsequence as cd rom ide1 ide1 than with a botable windows xp cd reinstall the entair operating system,by using computer foe a long period of time your os may be occured some errors or some files may be lost,