CORRECTION - I misread where you wrote "PC100", mistook it for
PC2100. That motherboard will not run PC100 memory in any
configuration, it simply is not supported on the MSI KT600
motherboards, it won't take DDR AND SDRAM (as-in, PC100/133)..
You need at least PC2100 memory for that board. The last
chipsets to support PC100 memory were (it's been a while but I
think these are right) Via KM266, Via KT133A, Sis 745.
Frankly, I would buy more memory before settling for thse older,
more limited tech motherboards, plus the PC100 memory would be
quire a bottleneck, even for a 1.8GHz Duron.