Help Problems with my memory

Hi I recently built a new computer. Here is what I have


Biostar mcp6p m2+
amd atholon 64 x2 4200+
350 watt psu
300 gig hard drive wd

Ok I have ram in slot one 1 gig of ddr2 pc2 6400 and my computer boots fine. originaly i had bought 2 sticks 512 dual ddr2 800 mhz model# kvr800d2k2/1gr and my computer would not boot. So I took one out of slot 2 and the computer booted. I tried to put just one sitck of ram in dimm slot 2 and it doesnt boot no post or anything.

Now when I take a stick of 512 dual ddr2 800 mhz model# kvr800d2k2/1gr and put it into slot two and have my 1gb stick in slot one I get a display but it freezes on post.

Im wondering if there is any bios settings i can set.
is it possible i have a bad dimm slot.

Thanks ahead of time for all your help