when i turn my dell inspiron 15 laptop sometimes it gone to black screen after showing dell startup logo and i can see mouse indicator also in black screen,then it may take 15 to 20 min to show the start up screen,my operating sys is windows 8.1,ram 4 gb and hdd 500 gb,sometimes it wont start then i have to turn the off button without proper shutdown ,,,,, whatz the cause /?i contacted dell support they told its problem with os