I have hp pavilion dv6 laptop I have problem that my laptop hang many time in a day I went to hp service center they told me that it is a problem in operating system so I install other copy of window but still I have same problem

What EXACTLY is the problem you are experiencing ?

What exactly do you mean by hang? WHat are you doing when it does this? WHat processes do you have running, how many background programs and utilities are running?

There are may things that can cause a PC to hang. I would rule out corrupt system files as you've reinstalled the OS and it still happens.

What are the specs of your laptop?

This isn't a cut-n-dry answer. THere will be a lot that goes into troubleshooting something that can be caused by so many different things!