ASUS, ABIT and MSI are good motherboards. Soltek also makes decent ones, but i heard Chaintech is something to be avoided. p4 2.8? That processor is quite new. Is this the comp that doesnt have mobo with agp slot? I thought that making of cheap mobos without agp slot stopped years ago.
I really like Albatron, but I broke my friend's mobo and gave him mine in a form of apology (I had built his comp with the same Albatron mobo I had) So for the time being, I'm on this outdated Shuttle. I may end up jumping straight to an athlon 64 instead of the mobile barton I was planning on getting.
PCI Express is completely different from Regular PCI in the shape and way it works. It isn't backwards compatible. There is one PCI Express slot (unless it's an Alienware) Andf then your regular PCI Slots. Hope that helps explain things. PCI Express right now is for Video Cards only.
As for what makes a good Motherboard. Pretty much it all depends. Of course you will need something P4 Compliant. Then what features you want and how much you are willing to pay. Motherboards aren't really an expensive thing considering what they do (I mean it's like the base of your computer!) So you can get some decent prices for some feature packed Mobo's.