I know nothing about intel. Far too expensive thats all I know. If you are upgrading your motherboard you will have to upgrade your memory and chances are your CPU, but as I said I know nothing about intel. I suggest going AMD. If you don't want an immediate purchase I would wait for 64Bit CPUs and mainboards to become mainstream - in the fall...

I agree with megatron...
but, if you want an immediate purchase...
I recently upgraded from an athlon XP 1800 to an athlon 2600+
512 SDram to 1GB DDR
The upgrade was very worth it
The motherboard I purchased was an EPoX 8RDA+
Very good board IMHO especially if your not a speedfreak overclocker ;)No offence intended

In most cases satan u wont be able to keep that SDram when upgrading your board unless you wanna go for one of those boards with the SDram and the DDRram

As far as the chip goes I would suggest an xp2500+ since they have just hit the price/performance sweetspot. The overclock well too! I recommend reading a review of a motherboard to first get a feel for it and then find more indepth detail in forums as you deem necessary.

ive got a 2500+
and its working damn good
and I over clocked it too 3200+ no problems,
not much heat increase either,

Check my system specs down below,

so you want gaming performance mobo and not too much on ocing right?

from the top of my head i cant suggest anything without knowing the budget line you're in but i can make some suggestions

buying a new motherboard can change depending on what type you get, if yer sticking with your p4 chip then you will likely go intel, but you can always change to amd if you're planning on buying a new cpu

High-end/Best Performance:
ASUSTeK followed by MSI (both fast, expensive)

Middle-end/Good Performance:
Abit(pretty good intel line), EPoX(pretty good intel line) and ECS (low-end, good performance always ECS )

Most Features/Good Performance:
Soyo (many features, good performance) and nForce2 (many features, good performance, great for games)

Pricetimation:
High: 100$-200$
Middle: 80$-150$
Features: 65$-180$

(the pricetimations are based on the highest or top model from the brands and are approx, not exact prices, research more before buying)

there are a lot of other brands out there, these are just the ones that are common to me

anyway good luck, need more suggestions just post your budget and what type of cpu you would like to use ie: (amd (lottsa cooling, good price), intel (average temp, expensive)) for a more approximate match :D

^^ what he said ^^

Your mainboard should be upgradeable with DDR-RAM

Get some decent DDR-400 RAM and remove your SDRAM - you should see some noticeable speed gain as SDR slows down the P4 a lot