According to this page: http://www.ezimobile.com.au/prod870.htm
your motherboard has:
" two SDR sockets that support up to 2GB non-ECC PC2700/PC2100/PC1600 or PC133/PC100 SDRAM DIMMs."
All this simply means is, you can have a maximum of 2 gigabytes of DDR ram or just straight SD ram.
In answer to your question about being able to take the DDR ram out and snapping in the SD ram, yes, you can do that and no you dont have to do anything special to activate it. Just that you cant have both ddr and sd ram in at the same time.
The ram doesnt have to go in any particular order, the only thing that can go wrong are incompatabilities with two different ram chips running at the same time, although this is rare.