I have the p4x400 ultra, and it it a very nice board.
However, I have ran into a few problems with it:
The first being that the onboard sound can cause random system crashes, disabling it through the bios solved the problem (but I had to buy a sound card). There may be updated drivers out for it.
The second thing is not realy a problem, but could be a slight bummer for the mad overclocker. Overclocking on this board is a bit limited, and the only deviders I have access to are the RAM deviders. Meaning that every device in the system is overclocked, not only the processor and the RAM.
Everything else works as expected, and flawlessly. I am running a P4 2.4b@2.7 at the moment, but I had been running at 2.84-2.86, durring the colder seasons (and when I only had one computer running in the room).
Once I move off stock cooling (may be awhile, as I have no $$$ at the moment), things should get a little faster.
Anyway, I do hope it isn't your processor
