Dell Studio 1558 Blue Screen Issue

I have installed Windows 8 on my laptop. I was using it for the past 1 year and didn't have any issues. Recently I bought a external monitor with HDMI connection. I used that for extending my laptop screen. I have also updated to latest display drivers just to avoid display issues.

After I started using that, I started getting message "Display driver stopped responding and has recovered" and then another error message came "Your PC restarted unexpectedly due to an unknown error, press OK to restart and try reinstalling windows". I have tried several times reinstalling windows 8 but problem stayed there. Error code : VIDEO_TDR_FAILURE.

After all these attempts, I have installed Windows 7 back in my laptop. Now I am getting another blue screen error message "A problem has been detected and windows has been shutdown to prevent damage to your computer".

Can anyone suggest a solution for this?

Thanks,

Subash