your Q6600 IS running at full speed. It shows up at a lower clock speed because of EIST (Speedstep) and C1E in the BIOS which help reduce power consumption while idle. It will automatically shoot up to 2.4GHz when the CPU is put under load. Disable these two options if you want it to show up at the real clock speed in cpuz. But they are better left enabled.
I cant find EIST (speedstep) in my bios, i found C1E and disabled it but i still have problem in cpuz (still showing 1600mhz instead 2400).Can someone tell me where to find EIST in my bios?(motherboard gigabyte p35)...