Need help with overclocking/modding my video card please help!

never done voltage mods myself so can't speak to you on those. However, only you can figure out your max overclock, as every card is different. From what i've heard others say, it looks like you have a pretty good overclock on an 8600GT. You can keep pushing it until you start to notice artifacting in games. Overclocking can help a little, but it never will drastically improve your framerate. Ususally, overclocking is only noticeable when you are running below 30 frames per second on stock settings. That said, you look like you're getting a really good overclock, so maybe it is helping you more.

ok ty for your reply

What I would use is ATITool. Using the scan for artifacts option while watching the temps. Very nice, built into one tool. Put all your frequencys at stock settings. Then increase your Core to what you currently have or maybe higher.Run the scan for artifacts. Sit there for about 10 minutes and watch for yellow artifacts to appear. If some appear lower your freq by 10Mhz/repeat until your artifact free. The reason you have to watch is sometimes it will artifact but ATITool wont report it. Now set your core to stock and OC your memory. Repeat the steps for core. Once you have found your max non-artifacting frequencies set both of them to those frequencies and you should be all set. Run 3DMark06 and see the results. Yes it does take quite a but of time. If you want to do a 'quicker' version just run the artifact test for about a minute, if you see artifacts lower by 20Mhz, then test again for a minute. Obviously this way produces less accurate results, but gets you in the ballpark quickly. Dont forget to watch temps.

I heard that Rivatuner is supposed to be the best OC utility. What is the difference between the 2? I also ''heard'' that Ntune stunk...........

I use RivaTuner for the actual stepping up of Mhz and watching temps when playing games. I use ATITool for it's nice artifact scan ability for stability AND a nice temp gage all in one when you just want to stress with one tool. I too have heard Ntune is no good, but never used it so I can't say.