I believe DC memory works best with matched pairs, ie the same size. I don't think there is such a thing as 1.5 Gb modules; I could be wrong. If your Vostro doesn't have 3 memory slots then I would stick with 2 Gb for now. 32-bit Windows can only use 3 Gb maximum.

My Precision M70 notebook BIOS displayed "Mode: Dual Channel" even when I only had 1 DDR2 DIMM. I think that notebook DDR2 memory works differently then desktop DDR2. Because, when I only had a single DDR2 DIMM installed in my OptiPlex 745 Desktop, the BIOS displayed "Mode: Single Channel"

 

Sounds simple to me.........2x 1gb + 2x 512mb.  4DIMMs

Sorry I misunderstood.  I'll bet this applies to your PC.  The G33 desktop chipset has a feature where chips of different capacities can be mixed and still get dual channel.  Find out the chipset model of your PC and then go to the Intel website and download the datasheet for it.  Let me know.

There's only 2 slots on that notebook. You should either go with 2 Gb (1+1) or 4 (2+2). Course 32-bit windows can only see 3. How much better 3 Gb (that circumvents dual-channel technology) is to 2 Gb of dual-chanel (in equal pairs) is unknown to me.

Greek to me but as long as you're happy. Thanks for sharing though. I wonder if the newer Inspiron line (read 1720) has that technology embedded ? May at some point want to go to the memory max.