Me again, the lost and confused one.

Still trying to build my super computer, I have now purchased the motherboard, an Asus P4S8X.
I intend to buy a Pentium 4 probably a 2.53GHz, but I'm abit confused as I keep seeing places that sell Genuine Intel Pentiums and something called Northwood ones, so whats the difference if anything and which is best?

A northwood pentium is just a revision of the Pentium chip that Intel make. All p4 2.53Ghz are going to be northwood cores, and all pentiums are going to be genuine intel pentiums (unless you are taking a wander down camden market )