1. Have you recently physically disconnected the wiring from your floppy drive? If so you may have re-connected it the wrong way round - it can be done on most floppy drives. Usually this also leads to the floppy LED being constantly on.
2. Is it present in the BIOS? You can usually get into the BIOS by hitting the delete key after boot up, or look for screen messages to tell you how to get into it. Then check that the floppy drive is enabled.
3. Changing the floppy driver isn't necessary, Windows will detect it on boot up if it is enabled in the BIOS and correctly installed.
4. If the BIOS says it's enabled and you are sure that the connection is correct then your drive has failed and needs to be replaced.