PC wont POST with extra RAM

[the_GIMP]

Hey.
I have a new board that has 6 slots (4 ddr2) (2 ddr3) i've got 2 x 1gb in 2 of the slots. when i put another 2 x 1gb in the other 2 slots it wont boot.
PC switches on for about to secs then switches off.

I've also a 512mb graphics card, 3 hdds, and 2 drives. PSU 400watt.

Would it be that the psu is not powerful enough?
I've heard XP has a limit of 4gb but it wont work with 3gb either. All Ram is of the same make and speed. (1GB Corsair Dominator DDR2)

If anybody can help I'd appreciate it.
Thanks

 

[Ritwik7]

It would be helpful if you could provide us with your exact system specs including manufacturer name and product details.

Also try using the RAM in pairs and check if the new pair you just put work by themselves.

Your PSU might be a little weak depending on your system.

 

[the_GIMP]

Thanks for the reply. Ive got an 800watt power supply and it still doesnt seem to boot. ive tried all the ram an the pc works with any 2 but wont work with 4 (4x1gb)

the board is ASUS P5QC
the RAM is Corsair Dominator 4 x 1gb pc-8500 ddr2

cpu Intel Quad Core
3 hdds

With 4 inserted or even 3 the pc turns on but jus stays with the fans going, theres no beeps an the monitor wont come on.

Would it be thats im using XP, I doubt it tho.

Anybody ever hear of this?
Thanks

 

[Ritwik7]

What are your recommended RAM timings and voltage? Try setting those correctly in the BIOS first. Also I'm presuming that your RAM modules are identical.

 

[RayRay]

I did find something about the motherboard

Combo Memory with DDR2 and DDR3 support!
Intel® P45 chipset
ASUS 8-phase Power Design
Dual-channel DDR3 1333MHz / DDR2 1066 MHz
100% High-quality Japan-made Conductive Polymer Capacitors! (5000hrs VRM, over 5 years operation lifespan)
ASUS EPU-6 Engine
ASUS Express Gate
ASUS Drive Xpert
VRD11.1 CPU support (backward support VRD10.X CPU)

about ram
seems to be the ram slots should be 1.8V

2 x DIMM, Max. 8 GB, DDR3 1333/1066/800 Non-ECC,Un-buffered Memory
4 x DIMM, max. 16GB, DDR2 1066 / 800 / 667 MHz, Non-ECC, Un-buffered memory
Dual channel memory architecture
When installing total memory of 4GB capacity or more, Windows® 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended
*DDR2 1066MHz DIMMs work only on the black slots for one DIMM per channel. Ensure to install the DDR2 1066MHz DIMMs ONLY on the BLACK slots!
**Refer to www.asus.com or this user manual for the Memory QVL(Qualified Vendors Lists).
*** When installing total memory of 4GB capacity or more, Windows® 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended.

more at

http://www.datakjeden.no/PartDetail.aspx?q=p:2030812;c:36123;r:dinpris;r:dinpris

scroll down a bit and all the info is in english.