My board is Rev 1.03.

I haven't checked the power supply as I've had the mobo stay powered up a handful of times but still with no video support. The green LED on the mobo stays lit up the whole time. Does that mean anything?

Btw I have both the 24-pin EATXPWR and 4-pin ATX12V power connectors connected.

There you go, according to ASUS "Only PCB R2.0(or higher) support Intel® Core™2 processor." Sorry, Pentium 4 or Pentium D is as far as you can go. Didn't know there were any rev1 boards still around, they lack the correct voltage regulator to supply the right voltage for the C2D CPUs.

You could try this work around:
1) boot with a p4 cpu
2) in manual OC, change the voltage to Core level.
3) swap the CPUs

I read one person claim that they did this successfully on another non core 945 board, I never personally tried this.

Once fitted with CPU (Intel D chip), RAM (2 x 1GB Geil) and 250GB Seagate SATA, power supply is switched on the green power led on the board is lit, but when I power up and wait for the boot screen the CPU fan runs for approx 4 seconds the winds back down and stops. I briefly see the ASUS splash screen on my monitor and that’s it. It won’t start up.

I’ve tried another CPU to see if the CPU was faulty but same thing happens, I’ve also tested the first CPU on another board and the CPU is fine, same tests with my RAM and my RAM is okay. I’ve also tried another power supply but still no luck.

I sent the mobo back to the supplier with the above info and they've since e-mailed me back telling me it booted up perfectly! What the ....

Could I upgrade to the current BIOS version for use with a Core 2 Duo?

maybe your case connectors are messed up, try booting it without a case (just bridge the "power switch" pins to start it up). Also, see if booting without a heatsink makes it start booting properly, a few seconds won't kill it, but turn it off after that.

I bridged the connectors, still same problem, I'll try with no heat sink when the mobo arrives back to me.

Well I finally got my hackintosh working.

OSX 10.4.9 (Uphuck 10.4.9 v1.2)
Asus P5LD2-VM (rev1.03)
Intel Pentium D935 (3.20 GHz) Dual Core Processor
2 Gig Geil PC 5300 Ram
250 Gig Seagate Sata HDD
On-board graphics GMA 950 working (1440x900)
Network (Ethernet) working