I was referencing Guide v1.6.1 on your site which appears to be a solid match to my hardware. To be more exact: Intel Quad 2.4ghz Q6600, Asus P5KPL-CM, AMI Bios (v0602, 2/24/09),Two 2gb DDR II 800 Kingston Memory (4gb) and a 512mb Radeon PCIe video card.
I'm a newbie with respect to overclocking. In looking at the screen shots found in Guide v1.6.1 and shots from other articles on the site, it appears my bios is lacking the adjustments necessary to even begin overclocking. Hopefully, I am wrong about this or, at least, there exists a workaround.
They might be in a different menu to the one in the guide. I have an AMI BIOS and my overclocking options are under the Cell Menu (what kind of name is that?). Guides are for reference only, unless you have the same board. But as I can't see your BIOS I can't possibly know where the options are hidden. They may even require a special key combination to unlock, but that's only something I've seen with Gigabyte boards.