ok this will take a while , are you sitting comfortably.
open Riva Tuner , under the MAIN tab click the CUSTOMISE arrow in the TARGET ADAPTER box.
In the resulting window click the HARDWARE MONITOR button (looks like a filmstrip with a magnifing glass)
In the window that opens click the SETUP tab
in the next window you will have a selection of monitors put a tick next to CORE CLOCK\GEOMETRIC DOMAIN , MEMORY CLOCK , CORE TEMPERATURE , CORE VID click APPLY
In the same window click the PLUGINS tab and make sure all the plugins are selected (it doesnt matter if you need them or not its easier just to select em jusyt in case) click OK then OK again to get back to your newly setup HARDWARE MONITOR this will now show in graph form all your settings such as temp vid card speed etc.
now for the onscreen display bit RIGHT CLICK each graph and select SETUP you will be presented with a new window near the bottom there is an ON SCREEN DISPLAY SETTINGS box put a TICK in that box and click ok , do this for each setting you have in your graph core vid core clock etc.
Nearly done , you'll notice your voltage probably isnt being detected properly so right click your CORE VID graph and select SETTINGS then at the bottom left click the MORE tab in the resulting window click AUTOSELECT then click OK
When your back to your GRAPH TABLE (monitor) RIGHT CLICK any setting and click SETUP when the resulting window appaears wait a sec or two till the RUN SERVER box appaears in the ON SCREEN DISPLAY SETTINGS bit you checked earlier then click the RUN SERVER tab then click OK
Leave Riva Tuner and your Graph running in the background , in your taskbar you should see another riva tuner symbol , thats your monitor.
start up a game and hey presto all is there to be seeen , you can also display framerates etc this way but it all gets too cluttered so stick with the basics for now.
So when your running a game and it starts to screw up you'll be able to see exactly what your voltage , core/memory speeds and temps are doing so you can rule out those probs. For example if your voltage drops when it starts screwing up you know its your PSU.
You can also change the colour and position of your on screen display but ill leave that to you to figure out
hope this helps
Darren