Right, PC1600 is the DDR equivalent of PC-100, PC2100 = PC133, PC2400 = PC150, PC2700 = PC166. So in order to run PC2100, you need to have one of the following: 1. PC2100 (or better) Module and a 266Bus Processor, 2. VERY good PC1600 Modules and a 266Bus Processor, 3. PC2100 Modules and a 200Bus processor on a mobo that lets you set memory speed @ 1/3 greater than bus speed.
Peace
John