Hey Guys. I have a question about memory that is probably very simple you most of you guys. Is ram interchangeable? Meaning, If I my pc is running pc 2700 and i have a pc 2100 stick laying around, would i be able to use the two together? If so, would the memory only run as fast as the 2100? Also, I have a rig with pc 133 and an old pc 100 stick. will they work together?