My Dell Studio 1535 laptop has dual boot Windows Vista Home Premium & Ubuntu 14.04.

Graphic: Intel 965GM

The problem now is that it occationally turns into black screen after using for a while, I tried to find the solution for month but no luck (I have tried with Linux Mint also, same problem).

I think its hardware is still working fine as it could work well on Windows Vista, no issue.

Please share if you know how to find the root cause or solution!

Many thanks