Before I was using Ati radeon hd 3870.
I cleaned all previous drivers with DriverCleaner and reinstalled driver of geForce 9800GT this time it went well. But again time I can not play some games like Assassins Creed. Blue screen showing some error with invalid reference comes out and PC reboots itself automatically.
I will try to switch to SP3 as soon as I have time to reinstall OS.