Hi
Got the same board as you, i would advise that you reset bios before anything. My experience is as follows.
I have 4gb of ram also, not the same as yours, i installed all the ram and got the system built etc, i came to power up but the cpu fan spun and then stopped, and then spun again but i got nothing on screen.
I then found out that this was some saftey feature regarding overclocking. Anyway, still nothing on screen, so i had a read up on some forums and reverted to installing one stick in the yellow ddr2 slot and got to the bios, from there i had to increase my ram voltages so i could get it to boot with all the ram. My ram is Patiot Extreme 6400. I just added ram 1 stick at a time untill i could boot and get vista installed.
It now runs fine and is stable, i have not overclocked it as i am waiting for a better cooler to arrive on friday.
Yours may just boot without problems but just incase it does not just try the above as it will probably be memory/board issues. During swapping my ram around until i got it to boot i also reset the bios everytime, i also made sure power was unplugged and monitor disconnected, just incase
May be worth a read at the top to, but these boards are past half way in the thread if you get other problems.
**EDIT**
Copied this from another site as this is what i had to do to get mine to boot with 4 gig.
1) power down, unplug your machine, and don your anti-static wrist strap
2) clear CMOS by shorting the jumpers ***
3) remove all but 1 stick of RAM, but re-seat the remaining stick
4) enter BIOS setup and "load setup defaults" then save via F10, reboot
5) enter BIOS setup, use the CTRL+F1, go into M.I.T. and set you SPD auto to manual.
6) set the timings manually as rated for your RAM or use SPD
as above, adjust your DDR2 overvoltage to +0.3 or +0.4 depending on RAM
7) test with one stick, then try 2, then 4
8) Check your values in PC Health
Good Luck
