Could you check the model of the motherboard?have a look on the actual board not from the operating system
D945GCL, is close to your board. I the manual for that it say you can go up to
Yours is an OEM board, so it depends what support your OEM decides to add.
If you wanted to take a risk you could try the Q6700 or even QX68001066Mhz FSB, you might be OK with the Pentium Dual Core E6600 3.06Ghz. You'd be easily able to go to X6800 Core2Duo 2.93Ghz.