PC fails to load with three memory sticks

[Dray]

Motherboard type: Gigabyte GA-P31-DS3L
it has 4 memory slots (2 red and 2 yellow)

I had 2x1G sticks of this type:
DIMM3: Mushkin 991529 (996529) 1 GB DDR2-800 DDR2 SDRAM (5-5-5-18 @ 400 MHz) (4-4-4-12 @ 266 MHz)

And recently bought a 2GB stick:
DIMM1: Samsung M3 78T5663QZ3-CF7 2 GB DDR2-800 DDR2 SDRAM (6-6-6-18 @ 400 MHz) (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz)

Tried to connect all 3 together in any possible way but my PC wouldn't start or
reboot before windows gets to load.
I tried to pull out the old 2x1GB sticks and just put the new 2GB one and it
worked perfectly.
Now i installed 1GB+2GB and it works great but
i bought the new stick in order to have 4GB total, not 3.

Any way i can fix this? maybe i'm doing something wrong?
or could it be a bios problem? my bios version is F8 (2 updates behind the latest version)

 

[Tmagic650]

All the memory sticks should be the same type and speed modules. Your speeds and manufacturers are different. Some motherboards are more sensitive to this than others

 

[Dray]

Than how come i can run the pc with the 2GB and 1GB? they're different types/speeds
the question is why i cant install all 3