do you know or can advise the best cheapest old or new intel motherboard which can run 3GHZ intel P4, intel Duo and quad and uses ddr2 ram with 4 dimm slots for upgrade to 8gb ram?
To be fair, you kinda of need to do your own research, specially on price and availability. But to point you in the right direction, the boards that will support P4s and Quad Cores will be the ones before the 3 series chiipset boards as the the 3 series dosen't support P4s. So you are lookin at the 975 chipset backwards, but then you are going to run into the problem of finding boards taht will be compatible with quad cores. There are some though, off the top of my head i would say the DQ965GF is a good choice, it will do P4s and Quad cores and you can get 8 Gb of RAM in it.
Hope this helps