I believe that there are three different lga775 sockets.
The oldest only goes up to P4HT 3.8, the second one only goes up to Pentium D,
and the third might be able to do C2D and maybe C2Q.
I hope for you that you have the latest one or if I'm incorrect,
and your board can't run a C2D if that's what you wish, then you'll need to upgrade a few things some being major.
So you might take into consideration a new build or new machine in general.
At least a new motherboard if you're bent on keeping that unit.
LGA 775 is LGA 775, its one socket.
The things that matter is the NB+BIOS, which varies according to each Mobo, there are Mobos that support all 775 Processors.
I believe i have a very old biostar motherboard, but i honestly am not sure how to identify it with all the names. As far as the cpu intel 06 pentium 4 is all i know. Thats just what i read when i removed the cpu. When i check the hardware on my comptuer properties it says Intel(R) Pentium(R) 4 Cpu 3.00 hhz 2.99gHz (hope that helps)