look first take a look at your motherboard manual and see if you motherboard suports duron 1.3(there should be a board were all suported cpu's are righten.
2)i dont now the names but at your position (1.3mh)the cpu must be like a chip with many legs or like a cartridge.
take a look at your cpu and the cpu that you want to buy and compare them.but if you motherboards manual says that your motherboard supports the cpu that you want to buy(1.3 gh duron) then you dont have any problem.i dont think the same cpu exist in the 2 types 0bove
Dont forget the retro games