help me to replace my vga

Assuming that your cpu is a Q8400 (going by the clock speed), I would get an HD7870XT. These are available for around €200. Make sure that you thoroughly remove the Nvidia drivers before installing the AMD drivers. This might also have been your problem with the HD6970.
 
You still don't make any sense to me. If you can't understand English very well, please ask someone who you know who does to formulate the question or find a tech forum in your native language. It's hard to help you this way.