Hi. I have a dell studio 1557 laptop model number  PP39L. I bought it on February 2010. It was working fine until yesterday. I was watching a video 
on Netflix inside Windows 7, suddenly  white and black stripes appeared on the screen and my computer froze. I turned off  the computer by holding down the power button. When I restarted the computer there was nothing on the screen.  I

Yesterday I created a 50 GB partition and installed Windows Vista Ultimate Edition in  that partition from a disk. I have two other partitions C and D. C is the partition where I have installed Windows 7, which is approximately 100 GB. D is where I keep all my files and it  is approximately 150 GB. Both C and D drives are around 40% full.

I found that someone has posted similar problem in dell studio 1557 forum (http://en.community.dell.com/support-forums/laptop/f/3518/p/19463842/20172375.aspx). I tried to solve the problem by following the steps mentioned by "Dell-Manpreet C" in the forum, but
nothing seems to work.

I am not sure if BIOS configuration could cause problems like this. I have set HDD password from BIOS. Also sometimes I enable and disable Speed option and Virtualization option in BIOS. I enable these two BIOS options only when I am using Virtual box in Windows 7. 

So far I have removed a RAM and  replaced with a another  Ram, and another hard disk, but it's still displaying nothing. I tried to use my hard disk in an HP laptop of a friend, but my hard disk is password protected from my computer's BIOS, so it displays an message telling to install an OS.

I will be really happy if some once could point me to the right direction. 

Thanks!