VoodooDan from HP here. Since I don’t know the particular build of your machine, here are just a few general steps that might help you out:
1. In the settings tab of rivatuner, check the option run at windows startup
2. In the power user tab set to 1 the entry enableclockcontrolcloning, which can be found under the group Riva\overclocking\global
You need to restart rivatuner in order for this setting to take effect. This way, rivatuner will overclock both GPUs to the same clocks speed. In many cases these are not always the same when a system is shipped or when using catalyst controls. By the way, in Rivatuner, it is also a good idea to go into global settings and increase the fan speed to over 50%.
I hope this helps. Let me know if it does, and if you have any other questions.