getting bsod in boot

[sal_rc]

I have four memory slots and it's a ddr2 board.I already have 2+1 GB memory installed.
Whenever I install memory in a new slot I get bsod for various errors

 

[Tradesman1]

What mobo, CPU and model #s of the DRAM, prob need increaseds to DRAM and MC voltages to try and get all to play nice 😉

 

[sal_rc]

I think it was the RAM cuz I used another module and it worked fine but nowca new problem.I'm using different models of 667mhz in dual channel mode but my RAM frequency is dropped to 337 MHz.
And what is dual channel BTW?