Nvidia 7600 GS how safe is my overclock?

That is a large overclock. What is the performance gain in games? If the gains aren't much I'd reset it back to factory overclocked speeds. I had a 7900GS and overclocked I would see some decent gains but I had an aftermarket cooler because the stock cooler was barely adequate as a paper weight. Generally when you see artifacts, you want to turn the clocks down until you don't see any more artifacts. There are never any guarantees when overclocking.

There is always a risk that is assumed anytime you take a product over it's factory set clocks.

As far as the fan goes, I'm not too sure. The fan on my old 7900GS had a very low duty cycle so I couldn't manually set it high because it would change eventually back. The GS series typically don't come with the best coolers. The GT and GTX series come with much better coolers but for a much higher cost.

All the GS series gpus, 7600gs, 7900gs, and 8800gs are great overclockers. For the most part they are lower clocked versions of their big brothers. As long as the temperatures don't increase a great deal and you don't get artifacts, then you'll be fine. Many older video cards didn't have fan speed control options. And forget about voltage mods unless you add a better cooler.

One thing I do notice is lag in control? In WOW, my mouse has instant response when I move it, but lets say I hover the mouse over a button, there's like a 1/4 second delay then the button lights up.

Whereas if I lower the resolution, when I move the mouse over a button it lights up immediately.

Yes I'm working on a new complete build as we speak.

i5-750, Radeon 5850... the card's just so hard to find right now, and I'm waiting for a non-california site that won't tax me