Re: Lga 775
LGA 775 is better and newer Extreme Edition and Pentium D support dual core and they all use LGA775. I would use the stock heatsink that comes with the Pentium 4 HT. Generally they do a good job with cooling, but if you plan on OCing it then perhaps an investment in aftermarket cooling is in order.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?