OK, I've finally decided that its not the right time for me to build an AMD system, so instead I'm going to upgrade.
Here is what I currently have:

P4 2.8 with 533 FSB. I *believe* that it is a P4B, but not certain.

A dell motherboard.

ATI x800 Pro Vid Card

Audigy 2 ZS Soundcard

768 in probably mismatched (I think some is DDR333 and some is DDR 400) crap RAM.

My MOBO is Dell.

I want to replace the MOBO and RAM. Obviously I need something with AGP 8x.

Questions:

1. If new MOBO supports FSB of 800 (while CPU only does 533) will I get any performance gain from using DDR400 memory (instead of DDR333)?

2. Will I get performance gains from using Dual Channel Memory, given the processor is a 533 FSB?

3. Whats a good MOBO? I was looking at the MSI "865G NEO2-PLS" i865G Chipset Motherboard for Intel Socket 478 CPU .... Is that overkill for a 533 FSB processor?

Thanks in advance.

Determine exactly what proc you have

Download and use this utility to determine exactly what CPU you have installed first.
http://downloadfinder.intel.com/scripts-df/proc/T8Clearance.asp?url=/7838/eng/pidenu03.msi

the utility has confirmed that the CPU is 2.8 mhz and runs on a 533 FSB.

It didn't tell me, or I couldnt' find, the product designation -- ie. P4 2.8B. However, I think the A has a 400 FSB (and doesn't come in 2.8) and the C has a 800 FSB and the E is the other chipset (Prescott) which I definitely don't have.

So ... is getting a MOBO with 800 FSB just pointless? Is getting DDR400 pointless? Is getting dual channel RAM pointless?

Many thanks!

Base your decision on the relevant variables

Since the proc. is only capable of running on a 533MHz FSB, the mobo it's installed in can't run at 800MHz - it will be configured to run at 533. Most new mobos are capable at running at multiple FSB speeds. The one reason you should consider getting one that runs at 800 as well as 533 is if you get a new proc. (upgrade) down the road that runs on a 800MHz FSB (assuming it's compatible with the mobo).

Memory:
The same logic should be applied with the memory. The faster memory "normally" can be installed in a mobo running a slower FSB and the momory will just clock down. You will be able to use that memory in a future mobo/proc combination running a 800MHz FSB if you upgrade in the future. If the mobo supports dual channel RAM, I would get it.

SO, it's your decision whether you save money now (find out how much it will actually be) by buying only what you need to make your system run, which is perfectly fine; OR spend a little more and have the freedom to use the parts in future, faster systems.

Hope this helps.

BTW, I just realized my dual channel memory was installed (by me, oops) in single channel style (both DIMMS in channel A). I changed it so DIMM 1 is in slot 1 for channel A and DIMM 2 is in slot 1 for channel 2 and I have noticed a nice performance increase. It pays to read the mobo manuals carefully.