Nope, as i found out from an APC article it seems like the older 775 socket mobo's won't be compatible because of some sort of small miniscule modification which needs to be done for them to be conroe compatible.
eg: Asus P5N32 SLI Se Deluxe is the conroe supportable mobo whereas the older Asus P5N32 SLI Deluxe isn't.
Quote from APC October 2006 issue: "Many board manufacturers need to re-jig the power routes on the motherboard to provide the lower voltages the Core 2 Duo needs."
That's all that needs to be done to make a mobo Core 2 Duo compatible...