An issue with laptop graphics

Hi before two years I've  bought dell inspiron n5010  and it was working perfectly any way before on week i had a problem which is when im running my laptop on win7 it boot's normally but when the windows is not workin it reboots again  i format  the laptop and i installed win7 iy works but with very bad graphics i've tried to install video card driver and bios updates but nothing works same problam so i changed my windows to win 8 it worked firstly with normal graphucs but when i tried to install video card driver it gaves me an error blue screen  with bad graphics (same as win 7 ) and it says (video card failure ) but when i boot my laptoo it gives me noraml graphics firstly but after that i gives me video card failure  or the screen lights turned on and of with black screen , i took the laptop to a public store and he told me that the motherboard needs to be changed but i didnt believe him so what do u think is it the motherboard on the video card or something else?  ...  this is a screenshot of the bad graphics on win7 ( )