Mobo Vs Ram...which 1 is the culprit ??

have a dg45id mobo which apparently has 4 ram slots of 2gigs 800mhz each '

lets name the 4 ram slots as a,b,c and d.

i have 2 ram sticks of transcend ddr2 800 mhz each

the prob starts here ...

1. if i install 1 ram stick in slot a or b....comp boots and works flawlessly
if i install either of these ram sticks in slot c and d....i get the beep sound and no display at all !

2.now if i install both the ram sticks in slot a and b then i get no display at all but no beep sound either

3.then if i remove my graphic card and keep the display to the onboard graphics with both the ram sticks in slots a and b.... then i do get the display but then if i boot my win 7..the comp restarts and on xp...i get BSOD with the foll error

driver_irql_not_less_or_equal

and at the bottom its wrritten

ACPI.sys_address BA77AA97 base at BA779000 Date Stamp 4117A27

i have no clue what this means ....experts pls pour in ur views...

4.Further...on the slots c and d ....if i put both the ram sticks i hear the beep sound.

5. then at times....if i keep my display on graphic card then then i dont get display most of the times...i have to remove nd reinsert the ram stick several times before i see the display...which is very frustrating..

6. on onboard graphics i get proper display as and when if i remove or add ram sticks...other than the bsod if both the ram sticks are together on slots a and b

i have run a memory diagonistics nd found no errors so far...

Now the question is what should i do....is Mobo at fault...or the graphic card...or the ram sticks

Noob ques : is it possible that i m not inserting the ram sticks properly...as far as i knw ...there is only one way in which the ram stick goes into the slot....right ?

Please put in ur views....i m gonna go 2moro to rma my mouse...pls let me knw if my mobo or ram are at fault....so that i can them along as well...

Thanx is the least i can say !!

looking forth for the solutions ...bare me for my limited knowledge