First, I'd recommend a different heatsink. The Noisecontrol Silverado will not allow you to overclock at all. The Alpha Pal8046 is the best choice at the moment, as it uses the four mounting holes around the socket, and provides the current best performance on the market. $35 for just the heatisnk (no fan), and $47 for the heatsink and a noisy fan from <A HREF="http://www.newegg.com/app/ViewProduct.asp?submit=manufactory&catalog=62&manufactory=1463&DEPA=1" target="_new">here</A>. A close second place would go to the Swiftech MCX462. It's $69 with a fan <A HREF="http://www.newegg.com/app/ViewProduct.asp?submit=manufactory&catalog=62&manufactory=1437&DEPA=1" target="_new">here</A>.
After that, there should be settings in your BIOS to change your multiplier (currently at 15) and front side bus speed (currently at 133). What brand of RAM do you have? That will be a major factor in your overclocking success.
Raise the front side bus slowly, increasing voltage (currently at 1.75v) at signs of instability. If 3dMark freezes, then you're either overclocked too high or your voltage isn't high enough.
<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>
Don't step in the sarcasm!