You need to put you ram sticks in slots 1 and 3.
And you will need to reset you're cmos.
Then you should be good to go.
But when you are booting up go ahead and go into you're bios again and make double shure thats you have everything ok.
Check Cpu boot strap set to 800
Under advanced chipset controls check you ram settings.
You will need to set the very first setting to manuel
Do not change any of the other values under that one.
Then on the bottom .
You will find you're GAT settings.
Leave them at auto but for the last 2.
Change them to disable.
Another thing Mushkin loves higher voltages.
So on you're first page in BIOS go down to bottom where you see
VDIMM voltage or something like that.
And change it to 2.8 or 2.9
This will give more stability to you're ram.
Under AGP setting make sure it is set to FIXED
66/33 i think.
And last but not least cheak to make sure the ram stick is seated all the way in slot

Maybe you should do that first:aok