If the drive worked before, look at the ribbon cable, the motherboard and the drive itself. All have Pin 1 configuration marks. Make sure the red mark on the ribbon (pin 1) goes to pin 1 on the motherboard. Some floppies do not have the mark - so try the cable both ways. If this doesn't work try a new cable.
I just replaced my motherboard with a used one of the same make/model/chipset, so bootup was quite easy. However, there's one problem: my floppy (A) drive isn't recognized. It doesn't light on startup, and isn't shown in Windows Explorer. (OS is Win98SE).
I'm sure one possible reason for this is a damaged/defective motherboard, but am hopeful there's another, less drastic, cause. Can someone please give me some insight as to what's causing this?
Also, am I correct in my understanding that the red stripe on the IDE ribbon cable goes to the outboard side of the floppy drive? My FD connector has alignment slots on both top and bottom, so I want to verify that I've installed the cable correctly.