how can i overclock core2duo e7400 currently running a 2.80 ghz?

[bigkiler5]

my motherboard is intel Dg31gl and ram is 2gb ddr2

 

[mactronix]

That's quite an old board is it in a pre built system like say a Dell or HP ? If so then you most probably cant overclock it as they tend to use locked Bios on those type of PC's.

If your motherboard has settings in the Bios to do so you need to adjust the front side bus settings and usually adjust the memory configuration also.
Your best bet by far is to look at a few reviews of the 7400 as these usually include a section on overclocking and then read some reviews on how to overclock the 7400.
After that if you are still unsure come back and then at least you will have some understanding of what is meant to be happening.

Mactronix