I have an asus P5ND2-SLI motherboard and want to know if it will support a core 2 quad cpu.  If not, what is the largest cpu it will support?  Thanks.

probably Pentium Extreme Edition im not too good with pentium processors im not sure if the pentuim D is better but if your gonna get a pentium processor then get one with hyper-treading and overclock it
https://usm.channelonline.com/maglo [...] M002467937
from the FSB and scoket specs it seems to be able to use core 2 duo and maybe quad but the compatible processors say only Pentium ones.

Maybe consider a better mobo?

^ ????
 
Did you even bother to look up the motherboard on Asus's website?
 
http://usa.asus.com/products.aspx? [...] 3=227&l4=0
 

 
As an NF4 chipset, it can't support any of the C2D/C2Q CPUs.  You will need to upgrade your motherboard if you want to upgrade your CPU.

the best CPU you could get is the Pentium Processor Extreme Edition 965
you would defenitly wanna upgrade your mobo.
right now the best cpu solution is to get a C2D and overclock the hell out of it.