|The CPUZ link you posted lists the board as: "MB Model : P4M89-M7A"|
I'll look at the other & post back.
OK, your board DOES support the Core 2 Duo & I just had a look at the BIOS chapter. Here's what you should try...I'm only going to address the settings that need to be changed to get your CPU running at the correct speed with the RAM running in sync.
Under AGP & P2P Bridge Control:
VGA Share Memory Size = disabled
Direct Frame Buffer = disabled
Under Performance Booster Zone:
DRAM Clock/Drive Control (press enter)
DRAM Clock = 266MHz
CPU CLOCK = 266MHz
Async PCIE CLOCK = 100MHz
CPU Clock Ratio = 8X
Spread Spectrum = disabled
Save your settings & exit, then run CPUZ again. I think you'll find your E6400 will be running at full speed (2.13GHz at 1066MHz FSB) with the RAM running in step at 266MHz (533MHz DDR).