Most older motherboards will not recognise ram at 128 unless it's the correct speed, you need to see if your motherboard supports it.
I just worked on a Gateway with the same problem.
I had to use pc 66 or it won't recognise it correctly.
Look for a Bios update.
Ram is suppose to be backword compatible and is, but pc 66 ram motherboards will not and cannot recognise pc 100 and pc 133 ram.