Upgrading HP d530 to fully optimise it

Hi am running a lower end pc with the following specification:-

HP Compaq, intel pentium 4, 3.0GHZ, 2.99GHZ, 640 mb ram, intel i845G card.

Am considering an upgrade but am lacking more detailed info on what devices to choose. So ma quiz are :

-Does my motherboard support dual core processors? If yes what type should i consider?
-Is there a lower end PCI graphics card that will deliver all beryl and aero features with a psu of 185W?
-What's the best and fastest DDR ram to go with? Or can DDR2/DDR3 be used on my machine?
-Last option; If the above proves futile, i'll consider swapping the whole motherboard but what's the best motherboad junked with advanced graphics card, DDR2/DDR3 ram, dual/quad processor and comes at a lower price? Also it should have a power range within 185W.

Geeks i need your help.

Manyenya

Manyenya,
How much do plan on spending for this upgrade and what type of computing do you participate in?
Are you a gamer, graphics person, or just the ordinary computing?
Might be less expensive to buy a whole new system than piece it together. IMHO

@Wolves, am a programmer and partial gamer, need4speed.

Then how much are you willing to spend in this upgrade process?
As a programmer and partial gamer you should know that all new incoming parts must be compatible with the leftovers.
That is why I keep asking for how much are you willing to part with?

Am willingng to spend atleast Ksh. 8000 only on this process.