Possible Duplicate:
What should I do when Ubuntu freezes?
My friend's computer is freezing. He is using a Samsung notebook with a 640 hard disk, 4GB of RAM, I3 second generation processor 2330. He is using Ubuntu 12.04. His system is freezing some times. The brightness symbol is came at top right, and it is blinking. Then, the system is freezing. We restarted the system, but the problem occurred again. Please tell me how can I solve the problem, step by step. Thank you.
