The other day i was using my computer and whilst writing a letter the computer just closed down and rebooted. Ithen tried to get back online which i did untill i tried to click on a website then it the computer just turned off and rebooted, and now things have just gone from bad to worse, when i try to boot up it comes on and gats as far as the windows logo with the blue bar flashing acreoss the bottom and then goes to a balck screen with just a white mouse arrow does anyone have a clue what this could be.