Will PC133 or PC100 memory work on a motherboard that has a 66 Mhz Front Side Bus (FSB)?

YES. In general, SDRAM is backward compatible and can run at bus speeds slower than that for which it is rated. For example, the 128 Mbytes of PC133 memory I have in my computer with an EpoX MVP3G2 Super 7 motherboard, which supports PC100 memory, works with a 100 Mhz FSB.. There are a few older 66 Mhz motherboards that will not work PC100 or PC133 memory, but they are exceptions, not the rule.