it's usually best to have identical modules, but if you are not going to be overclocking then you should be absolutely fine. I would put that Samsung stick in DIMM1, or whichever module is larger in DIMM1. dimms have to run at the same speed as each other, so i would guess that your mobo would set it to pc2100 speeds, but check in the BIOS after installation just incase it has changed at all. you should be fine.