Specs on your machine would help a great deal.

Single channel has nothing to do with SIMMs or DIMMS. Unless your machine is absolutely a fossil, you're going to be using some kind of DIMM. Dual channel is a way of increasing bandwidth. It's requirement is mobo support, and in the case of AMD systems, CPU support. Basically, it requires you to use only matched pairs, and gets you some extra bandwidth.

You're sure your system takes DDR1 and not DDR2, right? They are not compatible.